Update base64 requirement from 0.21 to 0.22 (Azure#1620)

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...v0.22.0)

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

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Author: dependabot[bot]

sdk/core/Cargo.toml

@@ -15,7 +15,7 @@ rust-version = "1.74.0"
 
 [dependencies]
 async-trait = "0.1"
-base64 = "0.21"
+base64 = "0.22"
 bytes = "1.0"
 dyn-clone = "1.0"
 futures = "0.3"