Kill misc::maintenance::aft5 class

Commit Ief22aa5fa6ec19dbe368f79392c74a507945e02a killed AFTv5 from
Wikimedia wikis. Do the same to the maintenance cronjob.

Remove the puppet code altogether, as the cronjob will be removed
manually from the one host it's instantiated.

Change-Id: If99c34b59af8bf8722acbb02e51256bc47fef84b