chore(deps): update base64 requirement from 0.21 to 0.22 (#209)

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...v0.22.1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

crates/rmcp/Cargo.toml

@@ -32,7 +32,7 @@ oauth2 = { version = "5.0", optional = true }
 schemars = { version = "0.8", optional = true, features = ["chrono"] }
 
 # for image encoding
-base64 = { version = "0.21", optional = true }
+base64 = { version = "0.22", optional = true }
 
 # for SSE client
 reqwest = { version = "0.12", default-features = false, features = [