Correct numerical regression in vision embeddings

[i3hz]

What does this PR do?

This PR fixes a numerical regression bug in the vision positional embedding calculation that was introduced between transformers versions v4.54.1 and v4.55.1. The original change was made to improve exportability but resulted in a slight floating point difference.
The fix was applied to the base modular files (modular_idefics2.py and modular_idefics3.py) and then propagated to all dependent models via make fix-copies.

Fixes #41190

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. Regression in SmolVLM results in different vision embeddings #41190
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Who can review

@zucchini-nlp

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: idefics2, idefics3, smolvlm