fix lint error

Author: seratch

tests/test_agent_runner_sync.py

@@ -142,7 +142,9 @@ async def agen():
 
     try:
         runner.run_sync(Agent(name="test-agent"), "input")
-        assert cleanup_markers == ["done"], "Async generators must be finalized after run_sync returns."
+        assert cleanup_markers == [
+            "done"
+        ], "Async generators must be finalized after run_sync returns."
     finally:
         fresh_event_loop_policy.set_event_loop(None)
         test_loop.close()