build(deps): bump base64 from 0.21.3 to 0.21.4

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](marshallpierce/rust-base64@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>

Cargo.toml

@@ -17,7 +17,7 @@ lightning-net-tokio = { git = "https://github.com/fiksn/rust-lightning" }
 lightning-persister = { git = "https://github.com/fiksn/rust-lightning" }
 lightning-background-processor = { git = "https://github.com/fiksn/rust-lightning", features = [ "futures" ] }
 lightning-rapid-gossip-sync = { git = "https://github.com/fiksn/rust-lightning" }
-base64 = "0.21.3"
+base64 = "0.21.4"
 # do not upgrade to bitcoon 0.30!
 bitcoin = "0.29.2"
 bitcoin-bech32 = "0.13.0"