Update error message when Accelerate isn't installed

[muellerzr]

What does this PR do?

This PR provides a bit more verbose error when accelerate isn't found on an install of transformers, as the Trainer (on PyTorch) requires Accelerate to be installed.

The error message was changed from:

ImportError: Using the Trainer with PyTorch requires accelerate: Run pip install --upgrade accelerate

To be:

Using the `Trainer` with `PyTorch` requires `accelerate>=0.19.0`: Please run `pip install transformers[torch]` or `pip install accelerate -U`

Fixes # (issue)

• no dependency package accelerate installed when we install transformers v4.29.1 #23323

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?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

@LysandreJik

(@sgugger when you are back)

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[sgugger]

Thanks for updating this!

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint.