Remove varnishkafka delivery errors check

The check is probably broken as it flaps all the time, in what is
probably a more permanent error.

In any case, it's been spamming us with alerts for two days now and we
know something's broken. Disable for now, fix later.

Change-Id: I76a122e7d57da01d058bba2432dc197fb9013bef
Merge "Remove varnishkafka delivery errors check" into production