tests (untranslated_entities): surface the errors

Messages are being output, but not as warnings or errors.
Tag them as warning in a format that GitHub is known to parse, to bring
them to the surface.

util/untranslated_entities.py

@@ -27,7 +27,7 @@ def main() -> int:
             slug = slugify(entity.name)
             if slug in translations:
                 print(
-                    f"{config}:{entity._config.__line__}: can use translation_key: {slug}"
+                    f"::warning file={config},line={entity._config.__line__}:: Entity can use translation_key: {slug}"
                 )
     return 0