[ci] Fix flaky request test

We used the wrong attribute , id instead of number, for identifying the
supersede checkbox. Since id and number are usually equal in our tests
this just failed seldomly.

src/api/spec/features/webui/requests_spec.rb

@@ -137,7 +137,7 @@
       click_link 'Submit package'
       fill_in 'targetproject', with: target_project.name
       fill_in 'description', with: 'Testing superseeding'
-      check("supersede_request_numbers#{bs_request.id}")
+      check("supersede_request_numbers#{bs_request.number}")
       click_button 'Ok'
       within '#flash-messages' do
         click_link 'submit request'