Create less records in random pagination tests

We make the tests considerably faster, we make them more robust against
changes in the number of records shown per page, and we generate enough
records so the chance of randomly getting the same results twice in a
row is extremely low.

spec/features/legislation/proposals_spec.rb

@@ -22,6 +22,8 @@ feature 'Legislation Proposals' do
 
   feature "Random pagination" do
     before do
+      allow(Legislation::Proposal).to receive(:default_per_page).and_return(12)
+
       create_list(
         :legislation_proposal,
         (Legislation::Proposal.default_per_page + 2),