[whisper] only trigger forced ids warning once (#30966)

src/transformers/models/whisper/generation_whisper.py

@@ -1133,12 +1133,12 @@ class WhisperGenerationMixin:
             forced_decoder_ids = config.forced_decoder_ids
 
         if forced_decoder_ids is not None and task is not None:
-            logger.info(
+            logger.warning_once(
                 f"You have passed task={task}, but also have set `forced_decoder_ids` to {forced_decoder_ids} which creates a conflict. `forced_decoder_ids` will be ignored in favor of task={task}."
             )
             forced_decoder_ids = None
         elif forced_decoder_ids is not None and language is not None:
-            logger.info(
+            logger.warning_once(
                 f"You have passed language={language}, but also have set `forced_decoder_ids` to {forced_decoder_ids} which creates a conflict. `forced_decoder_ids` will be ignored in favor of language={language}."
             )
             forced_decoder_ids = None