Fix Seq2SeqTrainingArguments docs (#16295)

* Indent Seq2Seq Train Args docs

* Add Args keyword to Seq2Seq Train Args docs

src/transformers/training_args_seq2seq.py

@@ -27,12 +27,13 @@ logger = logging.getLogger(__name__)
 @add_start_docstrings(TrainingArguments.__doc__)
 class Seq2SeqTrainingArguments(TrainingArguments):
     """
+    Args:
         sortish_sampler (`bool`, *optional*, defaults to `False`):
-        Whether to use a *sortish sampler* or not. Only possible if the underlying datasets are *Seq2SeqDataset* for
-        now but will become generally available in the near future.
+            Whether to use a *sortish sampler* or not. Only possible if the underlying datasets are *Seq2SeqDataset*
+            for now but will become generally available in the near future.
 
-        It sorts the inputs according to lengths in order to minimize the padding size, with a bit of randomness for
-        the training set.
+            It sorts the inputs according to lengths in order to minimize the padding size, with a bit of randomness
+            for the training set.
         predict_with_generate (`bool`, *optional*, defaults to `False`):
             Whether to use generate to calculate generative metrics (ROUGE, BLEU).
         generation_max_length (`int`, *optional*):