Correct @since for hooks in wp-admin/includes/plugin.php. see #25229.

git-svn-id: https://develop.svn.wordpress.org/trunk@25477 602fd350-edb4-49c9-b593-d223f7449a82
Correct @since for hooks in wp-includes/class-wp-admin-bar.php. see #25229.

git-svn-id: https://develop.svn.wordpress.org/trunk@25478 602fd350-edb4-49c9-b593-d223f7449a82