Fix config.load_defaults in railtie_spec.rb

spec/integration/rails/railtie_spec.rb

@@ -8,7 +8,7 @@
       let(:test_app) do
         Class.new(Rails::Application) do
           config.eager_load = false
-          config.load_defaults 7.1
+          config.load_defaults "#{Rails::VERSION::MAJOR}.#{Rails::VERSION::MINOR}"
         end
       end