Why this change?
The two tests being updated in question has been flaky on CI. However,
when using `be_forbidden`, the error message does not indicate what the
actual response code was making it hard for us to debug.
What does this change do?
Assert for the exact response status code we are expecting.
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.
This change both speeds up specs (less strings to allocate) and helps catch
cases where methods in Discourse are mutating inputs.
Overall we will be migrating everything to use #frozen_string_literal: true
it will take a while, but this is the first and safest move in this direction
