This brings some consistency to closing `</header>` tags in theme templates and ensures they all have an associated HTML comment. Props freewebmentor, mukesh27. Fixes #52328. Built from https://develop.svn.wordpress.org/trunk@49993 git-svn-id: http://core.svn.wordpress.org/trunk@49694 1a063a9b-81f0-0310-95a4-ce76da25c4cd