Bump black from 21.11b1 to 21.12b0 (#5496)

Bumps [black](https://github.com/psf/black) from 21.11b1 to 21.12b0.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](https://github.com/psf/black/commits)

---
updated-dependencies:
- dependency-name: black
  dependency-type: direct:development
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Dirk Groeneveld <dirkg@allenai.org>

dev-requirements.txt

@@ -7,7 +7,7 @@ flake8
 mypy==0.910
 
 # Automatic code formatting
-black==21.11b1
+black==21.12b0
 
 # Allows generation of coverage reports with pytest.
 pytest-cov