Update the banner for update-core.php that tells users they are set up for security updates to happen in the background.

"This site is set up to install security updates of WordPress automatically. Cool!"

Checkmark is a placeholder; we'll tinker with this further today.

see #22704.

Built from https://develop.svn.wordpress.org/trunk@25816


git-svn-id: http://core.svn.wordpress.org/trunk@25728 1a063a9b-81f0-0310-95a4-ce76da25c4cd
When a plugin enables Background Plugin	updates, don't deactivate the plugin during update as we require a browser to reactivate it afterwards. See #22704

Built from https://develop.svn.wordpress.org/trunk@25817


git-svn-id: http://core.svn.wordpress.org/trunk@25729 1a063a9b-81f0-0310-95a4-ce76da25c4cd