[T5] Adding `model_parallel = False` to `T5ForTokenClassification` and `MT5ForTokenClassification` (#30763)
* Adding model_parallel = False
* Revert "Adding model_parallel = False"
This reverts commit ba1d99976acb598824ce3347dbe7d848daa21e79.
* Trainer: circumvent error for model in which is_parallelizable is True but does not have model_parallel attribute