Bump the cargo group across 1 directory with 1 update

Updates the requirements on [tokio](https://github.com/tokio-rs/tokio) to permit the latest version.

Updates `tokio` to 1.36.0
- [Release notes](https://github.com/tokio-rs/tokio/releases)
- [Commits](tokio-rs/tokio@tokio-0.2.0...tokio-1.36.0)

---
updated-dependencies:
- dependency-name: tokio
  dependency-type: direct:production
  dependency-group: cargo-security-group
...

Signed-off-by: dependabot[bot] <support@github.com>

lambda-smtp-relay/Cargo.toml

@@ -26,5 +26,5 @@ rustls = "^0.16"
 serde = "^1.0"
 serde_derive = "^1.0"
 stderrlog = "^0.4"
-tokio = "^0.2"
+tokio = "^1.36"
 webpki-roots = "^0.19"