Update base64 requirement from 0.21 to 0.22

Updates the requirements on [base64](https://github.com/marshallpierce/rust-base64) to permit the latest version.
- [Changelog](https://github.com/marshallpierce/rust-base64/blob/master/RELEASE-NOTES.md)
- [Commits](marshallpierce/rust-base64@v0.21.0...v0.22.1)

---
updated-dependencies:
- dependency-name: base64
  dependency-type: direct:production
...

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

Cargo.toml

@@ -22,7 +22,7 @@ rustcrypto = ["aes", "cbc", "sha2", "hmac", "subtle"]
 features = ["fernet_danger_timestamps"]
 
 [dependencies]
-base64 = "0.21"
+base64 = "0.22"
 byteorder = "1"
 openssl = { version = "0.10", optional = true }
 getrandom = "0.2"