tools/unitctl: Bump the slab crate from 0.4.10 to 0.4.11

Bumps <https://github.com/tokio-rs/slab> from 0.4.10 to 0.4.11.

Fix Slab::get_disjoint_mut out of bounds.

Link: Release notes <https://github.com/tokio-rs/slab/releases>
Link: Changelog <>https://github.com/tokio-rs/slab/blob/master/CHANGELOG.md>
Link: Commits <tokio-rs/slab@v0.4.10...v0.4.11>
Signed-off-by: dependabot[bot] <[email protected]>
Signed-off-by: Andrew Clayton <[email protected]>

Author: dependabot[bot]