Feature/standardize opt model card

[JoestarGagan]

What does this PR do?

This PR standardizes and enhances the documentation for the OPT model card ('docs/source/en/model_doc/opt.md'). The goal is to align it with the updated model card template (as mentioned in issue-Model cards #36979) .

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.
  • **No, this was a self-initiated effort to standardize the OPT model card based on the general contribution guidelines for documentation, as it is a straightforward improvement. **
• 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?
  * **N/A - This is a documentation-only change to a markdown file. **

Key changes included:

• Aligned the model card to the current Hugging face template.
• Integrated new details regarding the quantization capabilities .
• Added specific, verified notes to clarify model behavior.
• Successfully passed make style and make docs locally to ensure formatting and documentation build integrity.

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.

@stevhliu (as this is a documentation update)

[stevhliu]

Thanks!

[JoestarGagan]

Hi @stevhliu, updated as per the suggestions

[stevhliu]

LGTM! 🚀

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.