Model card for mobilenet v1 and v2

[yuanjua]

What does this PR do?

As suggested in this issue - #36979 - this PR updates the documentation of the MobilenetV1 and V2 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?
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  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?

@stevhliu

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[stevhliu]

Cool, thanks for knocking out two models at once!

[stevhliu]

Just a few more comments to ensure v2 and v1 are the same

[yuanjua]

Thanks for the detailed review!

[stevhliu]

LGTM, thanks! 🤗

[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.