fix(mm): issue with deleting single file models

Author: psychedelicious

invokeai/app/services/model_install/model_install_default.py

@@ -372,7 +372,7 @@ def unconditionally_delete(self, key: str) -> None:  # noqa D102
         if model_path.is_file() or model_path.is_symlink():
             model_path.unlink()
             assert model_path.parent != self.app_config.models_path
-            os.rmdir(model_path.parent)
+            rmtree(model_path.parent)
         elif model_path.is_dir():
             rmtree(model_path)
         self.unregister(key)