github: workflow: test: Pin Python version to 3.11

Set the Python version explicitly instead of
relying on the default version provided by the runner.
This ensures that the Python version is supported
by Zephyr (at least for now).

Some windows runners are stuck at Python 3.9

Author: stadlero

.github/workflows/test.yml

@@ -10,6 +10,11 @@ jobs:
       fail-fast: false
 
     steps:
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.11'
+
       - name: Python version
         run: |
           python3 --version