Bump tokio from 1.39.3 to 1.40.0 in /rustclient/example (#244)

Bumps [tokio](https://github.com/tokio-rs/tokio) from 1.39.3 to 1.40.0.
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-1.39.3...tokio-1.40.0)

---
updated-dependencies:
- dependency-name: tokio
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

rustclient/example/Cargo.toml

@@ -4,5 +4,5 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
-tokio = { version = "1.39", features = ["macros", "rt-multi-thread"] }
+tokio = { version = "1.40", features = ["macros", "rt-multi-thread"] }
 karmen = { path = "../lib" }