Use markdown with gfm pipeline rather than gfm method

app/views/projects/commits/show.atom.builder

@@ -17,7 +17,7 @@ xml.feed "xmlns" => "http://www.w3.org/2005/Atom", "xmlns:media" => "http://sear
         xml.name commit.author_name
         xml.email commit.author_email
       end
-      xml.summary gfm(commit.description)
+      xml.summary markdown(commit.description, pipeline: :atom)
     end
   end
 end

app/views/projects/issues/_closed_by_box.html.haml

 .issue-closed-by-widget
   = icon('check')
-  This issue will be closed automatically when merge request #{gfm(merge_requests_sentence(@closed_by_merge_requests.sort))} is accepted.
+  This issue will be closed automatically when merge request #{markdown(merge_requests_sentence(@closed_by_merge_requests.sort), pipeline: :gfm)} is accepted.