fix ppo callbacks

src/llamafactory/train/ppo/workflow.py

@@ -22,7 +22,7 @@ from transformers import DataCollatorWithPadding
 from ...data import get_dataset
 from ...extras.ploting import plot_loss
 from ...model import load_model, load_tokenizer
-from ..callbacks import FixValueHeadModelCallback, fix_valuehead_checkpoint
+from ..callbacks import fix_valuehead_checkpoint
 from ..trainer_utils import create_ref_model, create_reward_model
 from .trainer import CustomPPOTrainer
 
@@ -59,7 +59,7 @@ def run_ppo(
         training_args=training_args,
         finetuning_args=finetuning_args,
         generating_args=generating_args,
-        callbacks=callbacks + [FixValueHeadModelCallback()],
+        callbacks=callbacks,
         model=model,
         reward_model=reward_model,
         ref_model=ref_model,