Comment 5 for bug 2024637

It turns out there was already an upload of apparmor 2.12-4ubuntu5.2 to bionic-proposed that got rejected (https://bugs.launchpad.net/ubuntu/+source/apparmor/+bug/1703821/comments/15), so this update will instead need to skip this version number and use 2.12-4ubuntu5.3 instead.