Just import torch AdamW instead (#36177)

* Just import torch AdamW instead

* Update docs too

* Make AdamW undocumented

* make fixup

* Add a basic wrapper class

* Add it back to the docs

* Just remove AdamW entirely

* Remove some AdamW references

* Drop AdamW from the public init

* make fix-copies

* Cleanup some references

* make fixup

* Delete lots of transformers.AdamW references

* Remove extra references to adamw_hf

examples/legacy/seq2seq/seq2seq_trainer.py

@@ -22,7 +22,6 @@ from transformers import PreTrainedModel, Trainer, logging
 from transformers.models.fsmt.configuration_fsmt import FSMTConfig
 from transformers.optimization import (
     Adafactor,
-    AdamW,
     get_constant_schedule,
     get_constant_schedule_with_warmup,
     get_cosine_schedule_with_warmup,
@@ -102,12 +101,11 @@ class Seq2SeqTrainer(Trainer):
                     "weight_decay": 0.0,
                 },
             ]
-            optimizer_cls = Adafactor if self.args.adafactor else AdamW
             if self.args.adafactor:
                 optimizer_cls = Adafactor
                 optimizer_kwargs = {"scale_parameter": False, "relative_step": False}
             else:
-                optimizer_cls = AdamW
+                optimizer_cls = torch.optim.AdamW
                 optimizer_kwargs = {
                     "betas": (self.args.adam_beta1, self.args.adam_beta2),
                     "eps": self.args.adam_epsilon,