Make an RSpec test consistent with the others of its type

- This was testing for `response.status` redirecting to a URL. I'm not
  sure how this worked, unless `redirect_to` passes its status code back
  and it was receiving that, but in any case it looks wrong at first
  glance, and we should be consistent with the other redirect_to tests
  in this file and others.
Merge pull request #401 from alphagov/make_an_rspec_test_consistent

Make an RSpec test consistent with the others of its type