Change branch .gitreview to point to this long-lived topic branch

This will cause "git review" to push to refs/for/wip/editorcampaigns.
Donno what will happen when you merge this topic to master, hopefully
it won't merge on top of .gitreview there.

Change-Id: I63d7739a01c1317311b2c90f5e2187f3935208f7