Remove smtp.wikimedia.org

As mark pointed out in 4fa1110, smtp.wikimedia.org was meant only for
authenticated submissions. I was led to believe it was still being used
by smokeping due to its (non-functional) configuration. That
configuration was amended in 07f985a62 so now we remove the non working
anymore record

Change-Id: I0902216c884cc45cc5535665829fbadc8c85499a
Merge "Remove smtp.wikimedia.org"