Bump ansible-lint from 6.18.0 to 6.21.0

Bumps [ansible-lint](https://github.com/ansible/ansible-lint) from 6.18.0 to 6.21.0.
- [Release notes](https://github.com/ansible/ansible-lint/releases)
- [Commits](ansible/ansible-lint@v6.18.0...v6.21.0)

---
updated-dependencies:
- dependency-name: ansible-lint
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

test-requirements.txt

@@ -1,4 +1,4 @@
-ansible-lint==6.18.0
+ansible-lint==6.21.0
 yamllint==1.32.0
 molecule-plugins[docker]==23.4.1
 molecule-plugins[lint]==23.4.1