tests: fix saved search index action test.

This passed in development but failed in CI because SavedSearch.redis
used the live Redis server, which worked by accident as long as you had
a Redis server running.

test/functional/saved_searches_controller_test.rb

@@ -5,6 +5,7 @@ class SavedSearchesControllerTest < ActionDispatch::IntegrationTest
     setup do
       @user = create(:user)
       @saved_search = create(:saved_search, user: @user)
+      SavedSearch.stubs(:redis).returns(MockRedis.new)
     end
 
     context "index action" do