fix: update test to handle behavior of latest Nokogiri

Author: flavorjones

test/integration/test_ad_hoc.rb

@@ -226,8 +226,7 @@ def test_dont_remove_whitespace_between_tags
 
         it "Loofah.document removes the comment" do
           sanitized = Loofah.document(html)
-          sanitized_html = sanitized.to_html
-          refute_match(/--/, sanitized_html)
+          refute(sanitized.children.any? { |node| node.comment? } )
         end
 
         it "Loofah.scrub_document removes the comment" do