Update hmac requirement from 0.10 to 0.11

Updates the requirements on [hmac](https://github.com/RustCrypto/MACs) to permit the latest version.
- [Release notes](https://github.com/RustCrypto/MACs/releases)
- [Commits](RustCrypto/MACs@hmac-v0.10.0...hmac-v0.11.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

postgres-protocol/Cargo.toml

@@ -13,7 +13,7 @@ base64 = "0.13"
 byteorder = "1.0"
 bytes = "1.0"
 fallible-iterator = "0.2"
-hmac = "0.10"
+hmac = "0.11"
 md-5 = "0.9"
 memchr = "2.0"
 rand = "0.8"