When a topic was published from a shared draft and it had tags, the
users watching the tags were not notified. The problem was that the
topics are usually created in a secret category and publishing it just
moves an existent topic to the target category, without making any
changes to the tags.
It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
