Remove top_p from gpt models (deprecated from GPT-5)

PiperOrigin-RevId: 808950671
Change-Id: I4eb46df3438ddaeeb15f3dad8abce3bd5473aa80

Author: DavidePaglieri

concordia/language_model/base_gpt_model.py

@@ -58,7 +58,7 @@ def _sample_text(
       timeout: float = language_model.DEFAULT_TIMEOUT_SECONDS,
       seed: int | None = None,
   ) -> str:
-    del terminators  # Unused for OpenAI models.
+    del terminators, top_p  # Unused for OpenAI models.
 
     messages = [
         {
@@ -90,7 +90,6 @@ def _sample_text(
         messages=messages,
         temperature=temperature,
         max_completion_tokens=max_tokens,
-        top_p=top_p,
         timeout=timeout,
         seed=seed,
         reasoning_effort=reasoning_effort,