Bump base64 from 0.21.3 to 0.21.4 (#568)

Bumps [base64](https://github.com/marshallpierce/rust-base64) from 0.21.3 to 0.21.4.
- [Changelog](https://github.com/marshallpierce/rust-base64/blob/master/RELEASE-NOTES.md)
- [Commits](https://github.com/marshallpierce/rust-base64/compare/v0.21.3...v0.21.4)

---
updated-dependencies:
- dependency-name: base64
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.lock

@@ -179,9 +179,9 @@ dependencies = [
 
 [[package]]
 name = "base64"
-version = "0.21.3"
+version = "0.21.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "414dcefbc63d77c526a76b3afcf6fbb9b5e2791c19c3aa2297733208750c6e53"
+checksum = "9ba43ea6f343b788c8764558649e08df62f86c6ef251fdaeb1ffd010a9ae50a2"
 
 [[package]]
 name = "bitflags"