Bump black from 21.4b1 to 21.4b2

Bumps [black](https://github.com/psf/black) from 21.4b1 to 21.4b2.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/master/CHANGES.md)
- [Commits](https://github.com/psf/black/commits)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

linter-requirements.txt

@@ -1,5 +1,5 @@
 bandit==1.7.0
-black==21.4b1
+black==21.4b2
 flake8==3.9.1
 isort==5.8.0
 pydocstyle==6.0.0