link for optimizer names (huggingface#32400)

* link for optimizer names

Add a note and link to where the user can find more optimizer names easily because there are many more optimizers than are mentioned in the docstring.

* make fixup

src/transformers/training_args.py

@@ -611,8 +611,9 @@ class TrainingArguments:
 
             The options should be separated by whitespaces.
         optim (`str` or [`training_args.OptimizerNames`], *optional*, defaults to `"adamw_torch"`):
-            The optimizer to use: adamw_hf, adamw_torch, adamw_torch_fused, adamw_apex_fused, adamw_anyprecision or
-            adafactor.
+            The optimizer to use, such as "adamw_hf", "adamw_torch", "adamw_torch_fused", "adamw_apex_fused", "adamw_anyprecision",
+            "adafactor". See `OptimizerNames` in [training_args.py](https://github.com/huggingface/transformers/blob/main/src/transformers/training_args.py)
+            for a full list of optimizers.
         optim_args (`str`, *optional*):
             Optional arguments that are supplied to AnyPrecisionAdamW.
         group_by_length (`bool`, *optional*, defaults to `False`):