Bump black from 20.8b1 to 21.12b0

Bumps [black](https://github.com/psf/black) from 20.8b1 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] <[email protected]>

Author: dependabot[bot]

poetry.lock

@@ -26,7 +26,7 @@ timy = "^0.4.2"
 
 [tool.poetry.dev-dependencies]
 pytest = "^6.2.2"
-black = "^20.8b1"
+black = "^21.12b0"
 isort = "^5.8.0"
 jedi = "^0.18.0"
 pytest-celery = "^0.0.0-alpha.1"