[tune](deps): Bump pymunk from 6.0.0 to 6.2.1 in /python/requirements/ml

Bumps [pymunk](https://github.com/viblo/pymunk) from 6.0.0 to 6.2.1.
- [Release notes](https://github.com/viblo/pymunk/releases)
- [Changelog](https://github.com/viblo/pymunk/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/viblo/pymunk/commits)

---
updated-dependencies:
- dependency-name: pymunk
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

python/requirements/ml/requirements_rllib.txt

@@ -16,7 +16,7 @@ kaggle_environments==1.7.11
 mlagents_envs==0.28.0
 # For tests on PettingZoo's multi-agent envs.
 pettingzoo==1.22.1; python_version >= '3.7'
-pymunk==6.2.1
+pymunk==6.4.0
 supersuit==3.7.0; python_version >= '3.7'
 # For tests on minigrid.
 minigrid==2.1.0