build: Bump slab from 0.4.8 to 0.4.9

Bumps [slab](https://github.com/tokio-rs/slab) from 0.4.8 to 0.4.9.
- [Release notes](https://github.com/tokio-rs/slab/releases)
- [Changelog](https://github.com/tokio-rs/slab/blob/master/CHANGELOG.md)
- [Commits](https://github.com/tokio-rs/slab/compare/v0.4.8...v0.4.9)

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

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

Cargo.lock

@@ -2018,9 +2018,9 @@ dependencies = [
 
 [[package]]
 name = "slab"
-version = "0.4.8"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6528351c9bc8ab22353f9d776db39a20288e8d6c37ef8cfe3317cf875eecfc2d"
+checksum = "8f92a496fb766b417c996b9c5e57daf2f7ad3b0bebe1ccfca4856390e3d3bb67"
 dependencies = [
  "autocfg",
 ]