test: OpenAIChatGenerator - fix flaky test (#9075)

Co-authored-by: Amna Mubashar <amnahkhan.ak@gmail.com>

Author: anakin87

test/components/generators/chat/test_openai.py

@@ -886,7 +886,7 @@ def __call__(self, chunk: StreamingChunk) -> None:
 
         # check that the completion_start_time is set and valid ISO format
         assert "completion_start_time" in message.meta
-        assert datetime.fromisoformat(message.meta["completion_start_time"]) < datetime.now()
+        assert datetime.fromisoformat(message.meta["completion_start_time"]) <= datetime.now()
 
         assert isinstance(message.meta["usage"], dict)
         assert message.meta["usage"]["prompt_tokens"] > 0