ci: add untranslated_entity checks to yamltests flow

This could probably be worked into the pytest test, but since there is
already a utility script for finding these, for now just reuse it to
ensure more do not creep in.

.github/workflows/yamltests.yml

@@ -35,4 +35,6 @@ jobs:
           python -m pip install --upgrade pip
           pip install -r requirements-dev.txt
       - name: Device configs check with pytest
-        run: pytest tests/test_device_config.py
+        run: |
+          pytest tests/test_device_config.py
+          python util/untranslated_entities.py