Change test as per Rails 5.1.3 change

We are going to assume that Rails is providing the correct behaviour
for this use case, so we change the test accordingly to make it pass.

Ref: rails/rails@ff7f4a7 rails/rails#29662
Close: #172

test/integration/engine_test.rb

@@ -6,10 +6,9 @@ class RoutingTest < ActionDispatch::IntegrationTest
   include RouteTranslator::ConfigurationHelper
 
   def test_with_engine_inside_localized_block
-    skip 'Regression with Rails 5.1.3. See #172'
     get '/engine_es'
     assert_response :success
-    assert_equal '/blorgh/posts', response.body
+    assert_equal '/es/blorgh/posts', response.body
   end
 
   def test_with_engine_outside_localized_block