Update tokio-tungstenite requirement from 0.20 to 0.21

Updates the requirements on [tokio-tungstenite](https://github.com/snapview/tokio-tungstenite) to permit the latest version.
- [Changelog](https://github.com/snapview/tokio-tungstenite/blob/master/CHANGELOG.md)
- [Commits](snapview/tokio-tungstenite@v0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: tokio-tungstenite
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

client/Cargo.toml

@@ -23,7 +23,7 @@ serde = "1.0"
 serde_json = "1.0"
 thiserror = "1.0"
 tokio = { version = "1.25", features = ["net", "sync"], optional = true }
-tokio-tungstenite = { version = "0.20", optional = true }
+tokio-tungstenite = { version = "0.21", optional = true }
 url = "2.3"
 wasm-bindgen = { version = "0.2", optional = true }
 wasm-bindgen-futures = { version = "0.4", optional = true }