Revert "Freeze the AppArmor kernel feature set too"

This reverts commit a6df2415, which is not
needed with AppArmor 3.0.8-1~bpo11+1, which sets features-file= again (that
looks like a mistake by the way, so I'll fix that on the Debian side,
and will create an issue to re-introduces the patch I'm reverting here
next time we update AppArmor).