message: Fix bad pluralisation on event list summary hidden message handling
diff: "%(oneUser)sremoved a message %(count)s times|other": "%(oneUser)sremoved %(count)s messages",
  "%(oneUser)sremoved a message %(count)s times|one": "%(oneUser)sremoved a message",
  "%(severalUsers)ssent %(count)s hidden messages|other": "%(severalUsers)ssent %(count)s hidden messages",
  - "%(severalUsers)ssent %(count)s hidden messages|one": "%(severalUsers)ssent %(count)s hidden messages",
  - "%(oneUser)ssent %(count)s hidden messages|other": "%(oneUser)ssent a hidden message",
  + "%(severalUsers)ssent %(count)s hidden messages|one": "%(severalUsers)ssent %(count)s a hidden message",
  + "%(oneUser)ssent %(count)s hidden messages|other": "%(oneUser)ssent %(count)s hidden messages",
  "%(oneUser)ssent %(count)s hidden messages|one": "%(oneUser)ssent a hidden message",
  "Including you, %(commaSeparatedMembers)s": "Including you, %(commaSeparatedMembers)s",
  "Including %(commaSeparatedMembers)s": "Including %(commaSeparatedMembers)s",
  