Update ModuleType.__file__ to be Optional (#6186)

Per the Python documentation, `ModuleType.__file__` is `Optional`: https://docs.python.org/3/reference/import.html#file__

stdlib/types.pyi

@@ -171,7 +171,7 @@ class SimpleNamespace:
 
 class ModuleType:
     __name__: str
-    __file__: str
+    __file__: str | None
     __dict__: dict[str, Any]
     __loader__: _LoaderProtocol | None
     __package__: str | None