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] <[email protected]>

requirements-testing.txt

@@ -3,7 +3,7 @@ pytest ~= 7.4
 pytest-cov ~= 4.1
 pytest-timeout ~= 2.1
 pytest-xdist ~= 3.3
-black ~= 23.7
+black ~= 23.9
 moto[all] ~= 4.2
 mypy == 1.5.0
 ruff ~= 0.0.288