Fix Trainer with remove_unused_columns=False (#11382)

* Fix Trainer with remove_unused_columns=False

* Typo

src/transformers/trainer.py

@@ -482,7 +482,7 @@ class Trainer:
 
     def _remove_unused_columns(self, dataset: "datasets.Dataset", description: Optional[str] = None):
         if not self.args.remove_unused_columns:
-            return
+            return dataset
         if self._signature_columns is None:
             # Inspect model forward signature to keep only the arguments it accepts.
             signature = inspect.signature(self.model.forward)