Update base64 requirement from 0.21 to 0.22 (#719)

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@v0.21.0...v0.22.0)

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

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

Cargo.toml

@@ -33,7 +33,7 @@ secp256k1 = { version = "0.28", features = ["recovery"], optional = true }
 once_cell = { version = "1.8.0", optional = true }
 
 ## HTTP
-base64 = { version = "0.21", optional = true }
+base64 = { version = "0.22", optional = true }
 bytes = { version = "1.0", optional = true }
 reqwest = { version = "0.11", optional = true, default-features = false, features = ["json"] }
 headers = { version = "0.4", optional = true }