Fix overwriting of published post meta when previewing footnote changes

[adamsilverstein]

Fixes bug discovered in #52988

What?

Why?

How?

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

[Mamaduka]

@adamsilverstein, just to clarify: this is a different bug discovered while working on #52988 and can be tested/merged separately + recommended to be backported into a minor release.

Are the above statements correct?

P.S. Can you also provide quick testing instructions?

[jorgefilipecosta]

I think we can merge this PR, update_post_meta is just an update_metadata call, with additional logic to in case of revisions update the original post instead of the revision.

	$the_post = wp_is_post_revision( $post_id );
	if ( $the_post ) {
		$post_id = $the_post;
	}

Here it seems we want to avoid that logic to have the possibility of having revisions for the footnones.

[jorgefilipecosta]

The change looks good to me 👍

[Mamaduka]

If the e2e fails again, it might require rebasing due to core changes. See #54452.

[adamsilverstein]

Rebased against trunk