Bump slab from 0.4.10 to 0.4.11 (#865)

Bumps [slab](https://github.com/tokio-rs/slab) from 0.4.10 to 0.4.11.
- [Release notes](https://github.com/tokio-rs/slab/releases)
- [Changelog](https://github.com/tokio-rs/slab/blob/master/CHANGELOG.md)
- [Commits](tokio-rs/slab@v0.4.10...v0.4.11)

---
updated-dependencies:
- dependency-name: slab
  dependency-version: 0.4.11
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Bigna Härdi <[email protected]>

Author: dependabot[bot]