CI: Pin Python to 3.11.x

On 3.12 we get the following failure:

  AttributeError: '_AnsiblePathHookFinder' object has no attribute 'find_spec'

Possibly ansible-core 2.12 is too old for Python 3.12.

Author: markgoddard

.github/actions/setup/action.yml

@@ -15,7 +15,7 @@ runs:
   steps:
     - uses: actions/setup-python@v3
       with:
-        python-version: 3.x
+        python-version: 3.11.x
         # Cache Python dependencies
         cache: pip