Reduce number of records in pagination tests

Creating more than 25 records isn't necessary to test pagination; we can
stub the number of records per page in a test.

On my machine we save about one second per test with these changes.

spec/features/admin/proposal_notifications_spec.rb

@@ -80,8 +80,8 @@ describe "Admin proposal notifications" do
   end
 
   scenario "Action links remember the pagination setting and the filter" do
-    per_page = Kaminari.config.default_per_page
-    (per_page + 2).times { create(:proposal_notification, :hidden, :with_confirmed_hide) }
+    allow(ProposalNotification).to receive(:default_per_page).and_return(2)
+    4.times { create(:proposal_notification, :hidden, :with_confirmed_hide) }
 
     visit admin_proposal_notifications_path(filter: "with_confirmed_hide", page: 2)