Under some conditions, replacing an `<img` with `![]()` can break rendering, and make the image disappear.
Context at https://meta.discourse.org/t/152801
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.
Mixing multisite and standard specs can lead to issues (e.g. when using `fab!`)
Disabled the (upcoming https://github.com/discourse/rubocop-discourse/pull/11) rubocop rule for two files that have thoroughly tangled both types of specs.
