Bump smallvec in /code-samples/serving/cloudevents/cloudevents-rust (#5046)

Bumps [smallvec](https://github.com/servo/rust-smallvec) from 1.4.0 to 1.8.0.
- [Release notes](https://github.com/servo/rust-smallvec/releases)
- [Commits](https://github.com/servo/rust-smallvec/compare/v1.4.0...v1.8.0)

---
updated-dependencies:
- dependency-name: smallvec
  dependency-type: indirect
...

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

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

code-samples/serving/cloudevents/cloudevents-rust/Cargo.lock

@@ -1733,9 +1733,9 @@ checksum = "c111b5bd5695e56cffe5129854aa230b39c93a305372fdbb2668ca2394eea9f8"
 
 [[package]]
 name = "smallvec"
-version = "1.4.0"
+version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c7cb5678e1615754284ec264d9bb5b4c27d2018577fd90ac0ceb578591ed5ee4"
+checksum = "f2dd574626839106c320a323308629dcb1acfc96e32a8cba364ddc61ac23ee83"
 
 [[package]]
 name = "snafu"