[TRTLLM-9295][fix] restore greedy sampling in _test_openai_chat_guided_decoding (#9178)

Signed-off-by: ixlmar <[email protected]>

Author: ixlmar

tests/unittest/llmapi/apps/_test_openai_chat_guided_decoding.py

@@ -375,6 +375,7 @@ def test_structural_tag(client: openai.OpenAI, model_name: str):
         model=model_name,
         messages=messages,
         max_completion_tokens=256,
+        temperature=0.0,
         response_format={
             "type": "structural_tag",
             "format": {