Update ruff requirement in the dev-dependencies group across 1 directory

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

Updates `ruff` to 0.15.6
- [Release notes](https://github.com/astral-sh/ruff/releases)
- [Changelog](https://github.com/astral-sh/ruff/blob/main/CHANGELOG.md)
- [Commits](astral-sh/ruff@0.15.5...0.15.6)

---
updated-dependencies:
- dependency-name: ruff
  dependency-version: 0.15.6
  dependency-type: direct:development
  dependency-group: dev-dependencies
...

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

Author: dependabot[bot]

requirements-dev.txt

@@ -1,4 +1,4 @@
 pre-commit~=4.5.1
-ruff~=0.15.5
+ruff~=0.15.6
 yamllint~=1.38.0
 zipp>=3.19.1 # not directly required, pinned by Snyk to avoid a vulnerability