Resolve failure in ee/spec/mailers/notify_spec.rb

This is an EE-specific test that was broken by
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20871.

ee/spec/mailers/notify_spec.rb

@@ -171,7 +171,7 @@ describe Notify do
         aggregate_failures do
           is_expected.to have_header('Message-ID', /\A<.*@#{host}>\Z/)
           is_expected.to have_header('In-Reply-To', "<#{route_key}@#{host}>")
-          is_expected.to have_header('References',  /\A<#{route_key}@#{host}> <reply\-.*@#{host}>\Z/ )
+          is_expected.to have_header('References',  /\A<reply\-.*@#{host}> <#{route_key}@#{host}>\Z/ )
           is_expected.to have_subject(/^Re: /)
         end
       end