Drop StaleDesc notifications

Only moria1 votes on the new flag. Treating it in the same way as BadExit...

  https://lists.torproject.org/pipermail/tor-consensus-health/2018-December/009451.html

consensus_health_checker.py

@@ -675,11 +675,11 @@ def has_similar_flag_counts(latest_consensus, consensuses, votes):
     for flag, count in flag_count.items():
       # Skipping check for the following flags because...
       #
-      #   * BadExit is only voted on by a few authorities.
+      #   * BadExit and StaleDesc is only voted on by a few authorities.
       #   * Running isn't voted on when an authority first starts up.
       #   * moria1 likes to experiment with the HSDir flag.
 
-      if flag in ('BadExit', 'Running', 'HSDir'):
+      if flag in ('BadExit', 'Running', 'HSDir', 'StaleDesc'):
         continue
 
       vote_count = authority_flag_count.get(flag, 0)