Bump smallvec from 1.8.0 to 1.9.0 in /src/rust/engine (#16072)
Bump smallvec from 1.8.0 to 1.9.0 in /src/rust/engine (#16072)

Bumps [smallvec](https://github.com/servo/rust-smallvec) from 1.8.0 to 1.9.0.
- [Release notes](https://github.com/servo/rust-smallvec/releases)
- [Commits](https://github.com/servo/rust-smallvec/compare/v1.8.0...v1.9.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>

Co-authored-by: dependabot[bot] <1c358da00a777d4e9898c1280ab801e2df165188@users.noreply.github.com>
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