pip: update ruff requirement in the pip-updates group (#224)

Updates the requirements on [ruff](https://github.com/astral-sh/ruff) to permit the latest version.

Updates `ruff` to 0.12.12
- [Release notes](https://github.com/astral-sh/ruff/releases)
- [Changelog](https://github.com/astral-sh/ruff/blob/main/CHANGELOG.md)
- [Commits](astral-sh/ruff@0.12.11...0.12.12)

---
updated-dependencies:
- dependency-name: ruff
  dependency-version: 0.12.12
  dependency-type: direct:production
  dependency-group: pip-updates
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

test-requirements.txt

@@ -1,4 +1,4 @@
-ruff~=0.12.11
+ruff~=0.12.12
 coverage>=4.0,!=4.4 # Apache-2.0
 stestr>=4.2.0 # Apache-2.0
 codespell