fix(ci): pin Python to 3.13 for docs build

Python 3.14 removed pkg_resources, which breaks
ansible_basic_sphinx_ext. Pin to 3.13 until the
upstream dependency is updated.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Felix Matouschek <fmatouschek@redhat.com>

.github/workflows/docs.yml

@@ -30,7 +30,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v6
         with:
-          python-version: 3.x
+          python-version: "3.13"
           cache: pip
 
       - name: Install doc dependencies