Update base64 requirement from 0.13.0 to 0.20.0

Updates the requirements on [base64](https://github.com/marshallpierce/rust-base64) to permit the latest version.
- [Release notes](https://github.com/marshallpierce/rust-base64/releases)
- [Changelog](https://github.com/marshallpierce/rust-base64/blob/master/RELEASE-NOTES.md)
- [Commits](marshallpierce/rust-base64@v0.13.0...v0.20.0)

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

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

Author: dependabot[bot]

Cargo.toml

@@ -17,7 +17,7 @@ authors = [
 [dependencies]
 async-trait = "0.1.57"
 rand = "0.8.5"
-base64 = "0.13.0"
+base64 = "0.20.0"
 sha2 = "0.10.6"
 hmac = "0.12.1"
 serde_json = "1.0.85"