Fixed OwlViTModel inplace operations
# What does this PR do?

This PR replaces the "/=" operator in OwlViTModel which causes an error in the backward pass with the non-inplace version.

Fixes #24525 

#24525 

## Who can review?

@ydshieh 

_The documentation is not available anymore as the PR was closed or merged._<|||||>@pasqualedem Could you apply the commit suggestions, then we can merge 🙏 Thanks.<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_24529). All of your documentation changes will be reflected on that endpoint.