Aligns `wp_head` action priority with Jetpack's Custom CSS. Amends [38829]. See #35395, #38672. Fixes #39270. Built from https://develop.svn.wordpress.org/trunk@39616 git-svn-id: http://core.svn.wordpress.org/trunk@39556 1a063a9b-81f0-0310-95a4-ce76da25c4cd