[FIX] Stop test failures, permissions issue, and failing auto-assign

[DESm1th]

This pull request addresses a few remaining github actions issues

• 432ce4a allows newer versions of nibabel to be installed. This fixes test failures that were happening because the outdated version of nibabel was referencing a numpy attribute that doesnt exist for newer versions of numpy.
• 74a2900 updates the run_tests code coverage comment step to use a different token with comment writing permissions to fix a permission error.
• e31adb9 updates how we auto assign code reviewers. The github actions pipeline is still often failing to correctly assign reviewers. This will instead use github teams + the code owners file to always assign me and then randomly assign two additional reviewers for datman PRs