[Gradient checkpoining] Update Wav2Vec scripts

[falcaopetri]

What does this PR do?

This PR makes the Wav2Vec scripts compatible with the changes introduced in #13657 regarding the gradient_checkpointing feature/argument.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline, Pull Request section?
• Was this discussed/approved via a Github issue or the forum? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

@stas00, @LysandreJik, @patrickvonplaten

[stas00]

FYI, this is a duplicate of #13964, but I think yours is better since mine doesn't change the flax example.

[falcaopetri]

Hi and sorry for the duplicate. I checked for similar issues but forgot to search for PRs.

Besides the missed flax example, #13964 possibly runs into this warning: Passing gradient_checkpointing to a config initialization is deprecated and will be removed in v5 Transformers.

The present PR follows the recommendation from Performance#Gradient Checkpointing.

[stas00]

No need to be sorry, I was just pointing to maintainers that there are 2 of the kind so it's easy to deal with them at once.

Further, #13877 moved wav2vec2 to supported examples, but for some reason these examples didn't get ported.

[falcaopetri]

Well noted, the addition of examples/pytorch/speech-pretraining got me confused.

As I understood, run_wav2vec2_pretraining_no_trainer.py is equivalent to examples/research_projects/wav2vec2/run_pretrain.py, but uses accelerate instead of the Trainer API.

Nonetheless, there seems to be some duplicated work in, e.g., argument parsing, dataset setup, and model instantiation. It is also not clear whether the notes in examples/pytorch/speech-pretraining also apply to examples/research_projects/wav2vec2/ (they probably do, so it would be nice to have them together).

[stas00]

@patrickvonplaten, we had 2 similar PRs. #13964 got merged

and this one has one more file covered that mine didn't.

I rebased it to incorporate the changes from the other PR.

[patrickvonplaten]

Thanks for updating the scripts!