[s2s] add config params like Dropout in Seq2SeqTrainingArguments (#7532)

examples/seq2seq/test_finetune_trainer.py

@@ -26,7 +26,7 @@ def test_finetune_trainer():
 def test_finetune_trainer_slow():
     # TODO(SS): This will fail on devices with more than 1 GPU.
     # There is a missing call to __init__process_group somewhere
-    output_dir = run_trainer(eval_steps=2, max_len="32", model_name=MARIAN_MODEL, num_train_epochs=3)
+    output_dir = run_trainer(eval_steps=2, max_len="128", model_name=MARIAN_MODEL, num_train_epochs=3)
 
     # Check metrics
     logs = TrainerState.load_from_json(os.path.join(output_dir, "trainer_state.json")).log_history