Update docs for `next/future/image` migration guide

[styfle]

Follow up to #39270 to make the props collapse to newlines

[leerob]

I'm not sure this would be the issue of how they're displayed on mobile, though. Should we try removing the table instead?

[styfle]

@leerob Do you like sections from the original #39270 commit better?

See Rendered Markdown →

[leerob]

I would suggest doing it like this:

Responsive

// next/image: <ImageLegacy src={src} layout="responsive" />
// next/image/future: Use `sizes` and `style` for the same behavior

<ImageFuture
  src={src}
  sizes="100vw"
  style={{ width: '100%', height: 'auto' }}
/>

[styfle]

@leerob are you suggesting using comments so the legacy code isn’t highlighted?

[leerob]

Correct - my thought is you're going here because you want to copy-paste the new version, so the code comment gives you the only one to reference.

[styfle]

Closing in favor of #39421