Bump slotmap from 1.0.5 to 1.0.6 (#3809)

Bumps [slotmap](https://github.com/orlp/slotmap) from 1.0.5 to 1.0.6.
- [Release notes](https://github.com/orlp/slotmap/releases)
- [Changelog](https://github.com/orlp/slotmap/blob/master/RELEASES.md)
- [Commits](https://github.com/orlp/slotmap/compare/v1.0.5...v1.0.6)

---
updated-dependencies:
- dependency-name: slotmap
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

polkadot/Cargo.lock

@@ -9199,9 +9199,9 @@ dependencies = [
 
 [[package]]
 name = "slotmap"
-version = "1.0.5"
+version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a952280edbecfb1d4bd3cf2dbc309dc6ab523e53487c438ae21a6df09fe84bc4"
+checksum = "e1e08e261d0e8f5c43123b7adf3e4ca1690d655377ac93a03b2c9d3e98de1342"
 dependencies = [
  "version_check",
 ]