chore(deps-dev): bump black from 21.6b0 to 21.7b0

Bumps [black](https://github.com/psf/black) from 21.6b0 to 21.7b0.
- [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)

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

Author: dependabot-preview[bot]

poetry.lock

@@ -132,7 +132,7 @@ nose = "1.3.7"
 pylint = "2.9.3"
 pep8 = "1.7.1"
 isort = "5.9.2"
-black = "21.6b0"
+black = "21.7b0"
 pre-commit = "2.13.0"
 pytype = "2021.6.17"
 pycln = "0.0.4"