Add a check that warmup_setps is either 0 or >= 1

[ymoslem]

What does this PR do?

Update training_args.py to add a check that warmup_setps is either 0 or >= 1. Otherwise, raise an error.

Before submitting

• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).

• [x] 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?

• trainer: @muellerzr and @pacman100