fix(genai): lint error

Author: msampathkumar

genai/text_generation/textgen_chat_stream_with_txt.py

@@ -16,7 +16,7 @@
 def generate_content() -> bool:
     # [START googlegenaisdk_textgen_chat_stream_with_txt]
     from google import genai
-    from google.genai.types import HttpOptions, GenerateContentConfig
+    from google.genai.types import HttpOptions
 
     client = genai.Client(http_options=HttpOptions(api_version="v1"))
     chat_session = client.chats.create(model="gemini-2.5-flash-preview-05-20")