chore(deps): bump slab from 0.4.6 to 0.4.7

Bumps [slab](https://github.com/tokio-rs/slab) from 0.4.6 to 0.4.7.
- [Release notes](https://github.com/tokio-rs/slab/releases)
- [Changelog](https://github.com/tokio-rs/slab/blob/master/CHANGELOG.md)
- [Commits](tokio-rs/slab@v0.4.6...v0.4.7)

---
updated-dependencies:
- dependency-name: slab
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>