Use describe on feature tests

The `type: :feature` is automatically detected by RSpec because these
tests are inside the `spec/features` folder. Using `feature` re-adds a
`type: :feature` to these files, which will result in a conflict when we
upgrade to Rails 5.1's system tests.

Because of this change, we also need to change `background` to `before`
or else these tests will fail.

spec/features/verification/verification_path_spec.rb

@@ -1,6 +1,6 @@
 require "rails_helper"
 
-feature "Verification path" do
+describe "Verification path" do
 
   scenario "User is an organization" do
     user = create(:user, verified_at: Time.current)