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

docs/source/en/main_classes/optimizer_schedules.md

@@ -22,9 +22,6 @@ The `.optimization` module provides:
 - several schedules in the form of schedule objects that inherit from `_LRSchedule`:
 - a gradient accumulation class to accumulate the gradients of multiple batches
 
-## AdamW (PyTorch)
-
-[[autodoc]] AdamW
 
 ## AdaFactor (PyTorch)