fix xml spec that was failing locally

Author: Jelkster

spec/integration/multi_xml/xml_spec.rb

@@ -1,7 +1,13 @@
 require 'spec_helper'
 
 describe Grape::Xml do
-  it 'uses multi_xml' do
-    expect(Grape::Xml).to eq(::MultiXml)
+  if Object.const_defined? :MultiXml
+    it 'uses multi_xml' do
+      expect(Grape::Xml).to eq(::MultiXml)
+    end
+  else
+    it 'uses xml_mini' do
+      expect(Grape::Xml).to eq(::ActiveSupport::XmlMini)
+    end
   end
 end