Check exact array contents instead of inclusion

We're using `eq` and `match_array` in most places, but there were a few
places where we were still checking each element is included in the
array. This is a bit dangerous, because the array could have duplicate
elements, and we wouldn't detect them with `include`.

spec/models/legislation/process_spec.rb

@@ -114,9 +114,7 @@ describe Legislation::Process do
       it "filters past" do
         past_processes = ::Legislation::Process.past
 
-        expect(past_processes).to include(process_3)
-        expect(past_processes).not_to include(process_2)
-        expect(past_processes).not_to include(process_1)
+        expect(past_processes).to eq [process_3]
       end
     end