Bump mimalloc from 0.1.30 to 0.1.31 in /dask_planner (#910)

Bumps [mimalloc](https://github.com/purpleprotocol/mimalloc_rust) from 0.1.30 to 0.1.31.
- [Release notes](https://github.com/purpleprotocol/mimalloc_rust/releases)
- [Commits](purpleprotocol/mimalloc_rust@v0.1.30...v0.1.31)

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

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

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

Author: dependabot[bot]