rm williams from site.pp,use iodine for otrs mail

per RT #5908 williams is still up, but not doing anything,
and about to be wiped.

nevertheless, it appears in exim conf, in a route_list for
OTRS mail. williams used to be ticket.wikimedia.org (OTRS)
in the past, and that is now iodine instead.

so i'm removing it and just speculating that it should also use
iodine here. needs confirmation from OTRS person to make sure

and put into decom.pp to remove from monitoring

Change-Id: I0f0aa46039319bc66ff7904788997377a42be972