Add paranthesis to correct the check. (#3658)

Author: pramodith

trl/trainer/grpo_config.py

@@ -558,7 +558,7 @@ def __post_init__(self):
         if self.generation_batch_size is None:
             self.generation_batch_size = self.per_device_train_batch_size * num_processes * self.steps_per_generation
 
-        if self.generation_batch_size % self.per_device_train_batch_size * num_processes != 0:
+        if self.generation_batch_size % (self.per_device_train_batch_size * num_processes) != 0:
             raise ValueError(
                 f"generation_batch_size ({self.generation_batch_size}) must be divisible by the global batch size "
                 f"({self.per_device_train_batch_size * num_processes})."