Update black requirement from ~=25.1 to ~=25.9

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@25.1.0...25.9.0)

---
updated-dependencies:
- dependency-name: black
  dependency-version: 25.9.0
  dependency-type: direct:development
...

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

Author: dependabot[bot]

dev-requirements.txt

@@ -1,5 +1,5 @@
 diff_cover
-black ~= 25.1
+black ~= 25.9
 pylint
 pep257
 pydocstyle