deps: update black requirement from >=25.11.0 to >=25.12.0 in /config

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@25.11.0...25.12.0)

---
updated-dependencies:
- dependency-name: black
  dependency-version: 25.12.0
  dependency-type: direct:development
...

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

Author: dependabot[bot]

config/requirements-dev.txt

@@ -2,7 +2,7 @@
 pytest>=8.4.2
 pytest-cov>=4.1.0
 pytest-mock>=3.15.1
-black>=25.11.0
+black>=25.12.0
 flake8>=6.1.0
 mypy>=1.20.2