Allow Revision History of a post to be viewed even if user doesn't have edit permissions

[ShadowXVII]

Some of my users find it useful to go back and see changes from previous versions of a page when editing other pages.

This can't be done unless the user has Edit permissions, even if they have Read permissions for a given post type.

The revisions.php should allow view-only access to the history if the user has read instead of redirecting them to the posts list edit.php.

[ShadowXVII]

Actually this might be a dupe of #40577