Our SafeMigrate system is designed to prevent tables/columns being dropped in pre-deploy migrations. Its regex-based detection was triggering incorrectly on `ALTER COLUMN DROP NOT NULL`.
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.