Bumps [smallvec](https://github.com/servo/rust-smallvec) from 0.6.10 to 1.2.0.
- [Release notes](https://github.com/servo/rust-smallvec/releases)
- [Commits](servo/rust-smallvec@v0.6.10...v1.2.0)

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