chore(deps): update black requirement from ~=23.7 to ~=23.9

Updates the requirements on [black](https://github.com/psf/black) to permit the latest version.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](psf/black@23.7.0...23.9.1)

---
updated-dependencies:
- dependency-name: black
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements-testing.txt

@@ -5,5 +5,5 @@ pytest-cov ~= 4.1
 pytest-xdist ~= 3.3
 twine ~= 4.0
 mypy ~= 1.5
-black ~= 23.7
+black ~= 23.9
 ruff ~= 0.0.287