Move redirection test to controller specs

We make the test faster and avoid a strange issue with `current_path` in
JavaScript tests.

We should probably have done this in commit ec1874325.

spec/system/legislation/processes_spec.rb

@@ -387,16 +387,6 @@ describe "Legislation" do
         expect(page).to have_content("There are no proposals")
       end
 
-      scenario "create proposal button redirects to register path if user is not logged in" do
-        process = create(:legislation_process, :in_proposals_phase)
-
-        visit legislation_process_proposals_path(process)
-        click_link "Create a proposal"
-
-        expect(page).to have_current_path new_user_session_path
-        expect(page).to have_content "You must sign in or register to continue"
-      end
-
       include_examples "not published permissions", :legislation_process_proposals_path
     end