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.
Previously email validations could fire when deleting posts if for
certain reasons any user validations fail on the user objects
This kind of condition could happen in core due to a corruption of a
user record, or via a plugin that introduces a new validation on User