Simplify translatable tests in admin section

These feature tests were taking too long, we can't run them for every
single model.

I'm taking the approach of using one different model for each test, but
in theory only using a few models covering every possible scenario
would be enough.

spec/features/admin/admin_notifications_spec.rb

@@ -8,11 +8,6 @@ describe "Admin Notifications" do
     create(:budget)
   end
 
-  it_behaves_like "edit_translatable",
-                  "admin_notification",
-                  "edit_admin_admin_notification_path",
-                  %w[title body]
-
   context "Show" do
     scenario "Valid Admin Notification" do
       notification = create(:admin_notification, title: "Notification title",