Bump black from 21.11b1 to 21.12b0 in /requirements

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>

Author: dependabot[bot]

requirements/dev-requirements.txt

@@ -3,7 +3,7 @@ Sphinx-Substitution-Extensions==2020.9.30.0
 Sphinx==4.3.1
 VWS-Test-Fixtures==2021.11.5.1
 autoflake==1.4
-black==21.11b1
+black==21.12b0
 check-manifest==0.47
 doc8==0.10.1
 docker==5.0.3