Fixed : Metaboxes overlap Block Editor's edit link popup

[narenin]

Fix: #64812

What?

This PR will fixed the Metaboxes overlap Block Editor's edit link popup issue, mentioned in 64812

Why?

This issue happening because of the z-index and this PR will add the z-index to fix the overlapping issue.

How?

I have added the z-index: -1 to metabox class edit-post-layout__metaboxes.

Testing Instructions

• Install and activate any plugin that adds meta boxes to the post page
• Create a new post
• Copy/paste the first five (5) paragraphs of Lorem Ipsum into the body, this should automatically create five paragraph blocks.
• Ensure that the metabox(es) is(are) expanded, extending the scroll height of the page.
• Scroll down so that the bottom of the editor where it meets the metaboxes are in the middle of the page.
• Highlight the last word with your mouse and then press CTRL + K to add a link, this reveals the link editor's popup box below the highlighted text and displays behind the metabox(es).

[github-actions]

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Co-authored-by: narenin <narenin@git.wordpress.org>

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[t-hamano]

Thanks for the PR.

This problem has been fixed in #63939. This fix will be available in the next minor WordPress release.

[github-actions]

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