fix: remove preset_reward_function from RLVR hyperparameters to prevent empty value being sent to service

Author: lucasjia-aws

sagemaker-train/src/sagemaker/train/rlvr_trainer.py

@@ -171,6 +171,9 @@ def _process_hyperparameters(self):
             if hasattr(self.hyperparameters, 'reward_lambda_arn'):
                 delattr(self.hyperparameters, 'reward_lambda_arn')
                 self.hyperparameters._specs.pop('reward_lambda_arn', None)
+            if hasattr(self.hyperparameters, 'preset_reward_function'):
+                delattr(self.hyperparameters, 'preset_reward_function')
+                self.hyperparameters._specs.pop('preset_reward_function', None)
             if hasattr(self.hyperparameters, 'data_path'):
                 delattr(self.hyperparameters, 'data_path')
                 self.hyperparameters._specs.pop('data_path', None)