The About page has a `<div>` that doesn't close. Also, `<hr>`s should self-close. `hackificator` complains about these things.

See #27881.

Built from https://develop.svn.wordpress.org/trunk@28477


git-svn-id: http://core.svn.wordpress.org/trunk@28304 1a063a9b-81f0-0310-95a4-ce76da25c4cd