Update black requirement from ==25.11.* to ==25.12.*

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:production
...

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

Author: dependabot[bot]

requirements-test.txt

@@ -1,4 +1,4 @@
-black==25.11.*
+black==25.12.*
 flake8==7.3.*
 isort==7.0.*
 moto[server,kms]==5.1.*