build(deps): bump once_cell from 0.2.4 to 0.2.6

Bumps [once_cell](https://github.com/matklad/once_cell) from 0.2.4 to 0.2.6.
- [Release notes](https://github.com/matklad/once_cell/releases)
- [Changelog](https://github.com/matklad/once_cell/blob/master/CHANGELOG.md)
- [Commits](https://github.com/matklad/once_cell/compare/v0.2.4...v0.2.6)

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

Cargo.lock

@@ -702,7 +702,7 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "0.2.4"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "parking_lot 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1409,7 +1409,7 @@ dependencies = [
  "hyper 0.12.33 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "once_cell 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "once_cell 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "openssl 0.10.24 (registry+https://github.com/rust-lang/crates.io-index)",
  "parser 0.1.0",
  "regex 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1657,7 +1657,7 @@ dependencies = [
 "checksum net2 0.2.33 (registry+https://github.com/rust-lang/crates.io-index)" = "42550d9fb7b6684a6d404d9fa7250c2eb2646df731d1c06afc06dcee9e1bcf88"
 "checksum nodrop 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "2f9667ddcc6cc8a43afc9b7917599d7216aa09c463919ea32c59ed6cac8bc945"
 "checksum num_cpus 1.10.1 (registry+https://github.com/rust-lang/crates.io-index)" = "bcef43580c035376c0705c42792c294b66974abbfd2789b511784023f71f3273"
-"checksum once_cell 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)" = "d584f08c2d717d5c23a6414fc2822b71c651560713e54fa7eace675f758a355e"
+"checksum once_cell 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "1824583b0e4dc0c1716eea4fb51a9ca2634943f0b07fd929e79af6aeb5a513cc"
 "checksum openssl 0.10.24 (registry+https://github.com/rust-lang/crates.io-index)" = "8152bb5a9b5b721538462336e3bef9a539f892715e5037fda0f984577311af15"
 "checksum openssl-probe 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "77af24da69f9d9341038eba93a073b1fdaaa1b788221b00a69bce9e762cb32de"
 "checksum openssl-sys 0.9.49 (registry+https://github.com/rust-lang/crates.io-index)" = "f4fad9e54bd23bd4cbbe48fdc08a1b8091707ac869ef8508edea2fec77dcc884"