cargo: bump base64 from 0.13.1 to 0.20.0

Bumps [base64](https://github.com/marshallpierce/rust-base64) from 0.13.1 to 0.20.0.
- [Release notes](https://github.com/marshallpierce/rust-base64/releases)
- [Changelog](https://github.com/marshallpierce/rust-base64/blob/master/RELEASE-NOTES.md)
- [Commits](https://github.com/marshallpierce/rust-base64/compare/v0.13.1...v0.20.0)

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

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

Cargo.toml

@@ -30,7 +30,7 @@ trust-dns-resolver = "0.22"
 tokio = { version = "1", features = ["fs", "rt-multi-thread", "macros"] }
 tokio-tar = { version = "0.3" } # TODO: integrate tokio into async-tar
 backtrace = "0.3"
-base64 = "0.13"
+base64 = "0.20"
 bitflags = "1.3"
 chrono = { version = "0.4", default-features=false, features = ["clock", "std"] }
 dirs = { version = "4", optional=true }