Bump black from 21.5b1 to 21.5b2

Bumps [black](https://github.com/psf/black) from 21.5b1 to 21.5b2.
- [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[bot] <support@github.com>

Author: dependabot[bot]

poetry.lock

@@ -11,7 +11,7 @@ python = "^3.9"
 invoke = "1.5.0"
 pytest = "6.2.4"
 
-black = { version = "^21.5b1", allow-prereleases = true }
+black = { version = "^21.5b2", allow-prereleases = true }
 codespell = ">=2.0.0"
 flake8 = "^3.9.2"
 pep8-naming = "^0.11.1"