chore: fix cli UT

PiperOrigin-RevId: 762734348

Author: seanzhougoogle

tests/unittests/cli/utils/test_cli.py

@@ -80,6 +80,9 @@ async def run_async(self, *a: Any, **k: Any):
       response = _Content("assistant", [_Part(f"echo:{text}")])
       yield types.SimpleNamespace(author="assistant", content=response)
 
+    async def close(self, *a: Any, **k: Any) -> None:
+      ...
+
   monkeypatch.setattr(cli, "Runner", _FakeRunner)