Tidy up DataHygiene::PublishingApiRepublisher
Tidy up DataHygiene::PublishingApiRepublisher

Whitehall::PublishingApi.republish no longer returns anything significant and
instead raises an exception if something that isn't publishable is passed in.

hotvulcan/whitehall,alphagov/whitehall,robinwhittleton/whitehall,YOTOV-LIMITED/whitehall,hotvulcan/whitehall,askl56/whitehall,askl56/whitehall,askl56/whitehall,ggoral/whitehall,ggoral/whitehall,alphagov/whitehall,robinwhittleton/whitehall,robinwhittleton/whitehall,alphagov/whitehall,askl56/whitehall,ggoral/whitehall,alphagov/whitehall,YOTOV-LIMITED/whitehall,ggoral/whitehall,hotvulcan/whitehall,robinwhittleton/whitehall,hotvulcan/whitehall,YOTOV-LIMITED/whitehall,YOTOV-LIMITED/whitehall