build(deps): bump smallvec in /cross-checks/zero-malloc

Bumps [smallvec](https://github.com/servo/rust-smallvec) from 0.6.4 to 0.6.14.
- [Release notes](https://github.com/servo/rust-smallvec/releases)
- [Commits](servo/rust-smallvec@v0.6.4...v0.6.14)

---
updated-dependencies:
- dependency-name: smallvec
  dependency-version: 0.6.14
  dependency-type: indirect
...

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Author: dependabot[bot]