Extend lint test to test/ directory (#13247)

test/srt/openai_server/basic/test_serving_completions.py

@@ -6,7 +6,7 @@ Run with:
 
 import unittest
 from typing import Optional
-from unittest.mock import AsyncMock, Mock, patch
+from unittest.mock import AsyncMock, Mock
 
 from sglang.srt.entrypoints.openai.protocol import CompletionRequest
 from sglang.srt.entrypoints.openai.serving_completions import OpenAIServingCompletion