fix: remove a use of | in type annotations that slipped through

tests/validate/test_facades.py

@@ -96,7 +96,7 @@ def generate_client_facades(cls, project_root: Path) -> ClientFacades:
         return client_facades
 
     @staticmethod
-    def _try_import(module_name: str) -> ModuleType | None:
+    def _try_import(module_name: str) -> Optional[ModuleType]:
         try:
             return importlib.import_module(module_name)
         except NameError as e: