[docs] updated roberta model card

[allmight05]

What does this PR do?

As suggested in this issue - #36979 - this PR updates the documentation of the Roberta model, which will now be aligned with the standardized format for all the docs.

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.

@stevhliu would you please review my PR?

[stevhliu]

Thanks for your update, very clean! ✨

[allmight05]

@stevhliu need support on this issue

[allmight05]

@stevhliu I think the error is associated with npm package installation process during the documentation build. Can you please check it?

[stevhliu]

Thanks, I'll take a look and merge it for you when it gets fixed!

[allmight05]

@stevhliu so, there is no issues at my end right?

[stevhliu]

Nope, I'll take care of this for you and you don't need to do anything else!

[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.