Remove dependencies that were listed twice

Thanks, cargo-udeps! These two dependencies must have been accidentally left over when the 'dns' crate split from the 'dog' crate.

Cargo.lock

@@ -120,8 +120,6 @@ version = "0.1.0"
 dependencies = [
  "byteorder 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "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)",
 ]
 
 [[package]]

dns/Cargo.toml

@@ -12,7 +12,3 @@ log = "0.4"
 
 # protocol parsing
 byteorder = "1.3"
-
-# json
-serde = "1.0"
-serde_json = "1.0"