Update bytes requirement from ~0.5 to ~0.6

Updates the requirements on [bytes](https://github.com/tokio-rs/bytes) to permit the latest version.
- [Release notes](https://github.com/tokio-rs/bytes/releases)
- [Changelog](https://github.com/tokio-rs/bytes/blob/master/CHANGELOG.md)
- [Commits](tokio-rs/bytes@v0.5.0...v0.6.0)

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

Cargo.toml

@@ -15,7 +15,7 @@ edition = "2018"
 async-trait = "0.1.21"
 base64 = "~0.13.0"
 base64-serde = "~0.6.1"
-bytes = "~0.5"
+bytes = "~0.6"
 serde = { version = "~1.0", features = ["derive"] }
 serde_json = "~1.0"
 # default features force a dependency on openssl-sys, which we want to avoid for embedded applications