deps: update base64 requirement from 0.21.5 to 0.22.1

Updates the requirements on [base64](https://github.com/marshallpierce/rust-base64) to permit the latest version.
- [Changelog](https://github.com/marshallpierce/rust-base64/blob/master/RELEASE-NOTES.md)
- [Commits](marshallpierce/rust-base64@v0.21.5...v0.22.1)

---
updated-dependencies:
- dependency-name: base64
  dependency-version: 0.22.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

sare-core/Cargo.toml

@@ -37,4 +37,4 @@ sha3 = "0.10.8"
 tiny-bip39 = { version = "2.0.0", default-features = false }
 
 [dev-dependencies]
-base64 = "0.21.5"
+base64 = "0.22.1"