build(deps): bump base64 from 0.13.1 to 0.21.0

Bumps [base64](https://github.com/marshallpierce/rust-base64) from 0.13.1 to 0.21.0.
- [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@v0.13.1...v0.21.0)

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

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

Author: dependabot[bot]

Diff for: Cargo.lock

@@ -9,7 +9,7 @@ anyhow = { version = "1.0.66", default-features = false, features = ["std"] }
 askama = { version = "0.11.1", default-features = false }
 axum = { version = "0.5.17", default-features = false, features = ["headers", "json", "multipart", "query"] }
 axum-extra = { version = "0.3.7", default-features = false, features = ["cookie"] }
-base64 = { version = "0.13.1", default-features = false }
+base64 = { version = "0.21.0", default-features = false }
 clap = { version = "4.1.6", default-features = false, features = ["derive", "error-context", "help", "std", "usage", "wrap_help"] }
 confargs = { version = "0.1.1", default-features = false }
 enarx-config = { version = "0.6.1", default-features = false }