Bump tokio in /code-samples/community/serving/helloworld-rust (#6246)

Bumps [tokio](https://github.com/tokio-rs/tokio) from 1.33.0 to 1.38.2.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-1.33.0...tokio-1.38.2)

---
updated-dependencies:
- dependency-name: tokio
  dependency-version: 1.38.2
  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]

code-samples/community/serving/helloworld-rust/Cargo.lock

@@ -6,5 +6,5 @@ publish = false
 
 [dependencies]
 hyper = { version = "0.14.27", features = ["full"]}
-tokio = { version = "1.33.0", features = ["macros", "rt-multi-thread"] }
+tokio = { version = "1.38.2", features = ["macros", "rt-multi-thread"] }
 pretty_env_logger = "0.5.0"