Fix seq2seq example test (#7518)

* Fix seq2seq example test

* Fix bad copy-paste

* Also save the state

src/transformers/trainer.py

@@ -601,6 +601,7 @@ class Trainer:
             output_dir = os.path.join(self.args.output_dir, f"{PREFIX_CHECKPOINT_DIR}-{self.state.global_step}")
             self.save_model(output_dir)
             if self.is_world_master():
+                self.state.save_to_json(os.path.join(output_dir, "trainer_state.json"))
                 torch.save(self.optimizer.state_dict(), os.path.join(output_dir, "optimizer.pt"))
                 torch.save(self.lr_scheduler.state_dict(), os.path.join(output_dir, "scheduler.pt"))