Fix a writing issue in the comments of trainer.py (#14202)

src/transformers/trainer.py

@@ -244,7 +244,7 @@ class Trainer:
             detailed in :doc:`here <callback>`.
 
             If you want to remove one of the default callbacks used, use the :meth:`Trainer.remove_callback` method.
-        optimizers (:obj:`Tuple[torch.optim.Optimizer, torch.optim.lr_scheduler.LambdaLR`, `optional`): A tuple
+        optimizers (:obj:`Tuple[torch.optim.Optimizer, torch.optim.lr_scheduler.LambdaLR]`, `optional`): A tuple
             containing the optimizer and the scheduler to use. Will default to an instance of
             :class:`~transformers.AdamW` on your model and a scheduler given by
             :func:`~transformers.get_linear_schedule_with_warmup` controlled by :obj:`args`.