[Trainer] Undo #29896 (#30129)

* Undo

* Use tokenizer

* Undo data collator

docs/source/en/tasks/video_classification.md

@@ -407,7 +407,7 @@ Then you just pass all of this along with the datasets to `Trainer`:
 ...     args,
 ...     train_dataset=train_dataset,
 ...     eval_dataset=val_dataset,
-...     image_processor=image_processor,
+...     tokenizer=image_processor,
 ...     compute_metrics=compute_metrics,
 ...     data_collator=collate_fn,
 ... )