chore: post 6.3.1 release tasks

[aucampia]

Summary of changes

Checklist

• Checked that there aren't other open pull requests for
  the same change.
• Checked that all tests and type checking passes.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[coveralls]

Coverage: 90.782%. Remained the same when pulling 0697e80 on aucampia:iwana-20230319T1521-post_release into f3d31b0 on RDFLib:main.