build(deps): bump tokio from 0.2.20 to 0.2.21

Bumps [tokio](https://github.com/tokio-rs/tokio) from 0.2.20 to 0.2.21.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](https://github.com/tokio-rs/tokio/compare/tokio-0.2.20...tokio-0.2.21)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Cargo.lock

@@ -405,7 +405,7 @@ dependencies = [
  "indexmap 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "slab 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-util 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -489,7 +489,7 @@ dependencies = [
  "net2 0.2.34 (registry+https://github.com/rust-lang/crates.io-index)",
  "pin-project 0.4.16 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tower-service 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "want 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -502,7 +502,7 @@ dependencies = [
  "bytes 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "hyper 0.13.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "native-tls 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-tls 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -848,7 +848,7 @@ dependencies = [
  "bytes 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "native-tls 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-postgres 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-tls 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1020,7 +1020,7 @@ dependencies = [
  "serde_json 1.0.53 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_urlencoded 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-tls 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen 0.2.56 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1236,7 +1236,7 @@ dependencies = [
 
 [[package]]
 name = "tokio"
-version = "0.2.20"
+version = "0.2.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bytes 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1281,7 +1281,7 @@ dependencies = [
  "pin-project-lite 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "postgres-protocol 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "postgres-types 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-util 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -1291,7 +1291,7 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "native-tls 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1304,7 +1304,7 @@ dependencies = [
  "futures-sink 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "pin-project-lite 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1317,7 +1317,7 @@ dependencies = [
  "futures-sink 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "pin-project-lite 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1358,7 +1358,7 @@ dependencies = [
  "serde 1.0.110 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.53 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_path_to_error 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-postgres 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.5.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1759,7 +1759,7 @@ dependencies = [
 "checksum termcolor 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bb6bfa289a4d7c5766392812c0a1f4c1ba45afa1ad47803c11e1f407d846d75f"
 "checksum thread_local 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "d40c6d1b69745a6ec6fb1ca717914848da4b44ae29d9b3080cbee91d72a69b14"
 "checksum time 0.1.43 (registry+https://github.com/rust-lang/crates.io-index)" = "ca8a50ef2360fbd1eeb0ecd46795a87a19024eb4b53c5dc916ca1fd95fe62438"
-"checksum tokio 0.2.20 (registry+https://github.com/rust-lang/crates.io-index)" = "05c1d570eb1a36f0345a5ce9c6c6e665b70b73d11236912c0b477616aeec47b1"
+"checksum tokio 0.2.21 (registry+https://github.com/rust-lang/crates.io-index)" = "d099fa27b9702bed751524694adbe393e18b36b204da91eb1cbbbbb4a5ee2d58"
 "checksum tokio-macros 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "f0c3acc6aa564495a0f2e1d59fab677cd7f81a19994cfc7f3ad0e64301560389"
 "checksum tokio-postgres 0.5.4 (registry+https://github.com/rust-lang/crates.io-index)" = "d56010a704311361b7c9e870aaa4ddffaf9f2db89cbcf3e14773ac8a14469c9c"
 "checksum tokio-tls 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "9a70f4fcd7b3b24fb194f837560168208f669ca8cb70d0c4b862944452396343"