message: remove(types): System user flag
  Reference:
  BREAKING: The flag "System" has been removed from the documentation on 9 April 2021
diff: @@ -10,7 +10,6 @@ export enum DiscordUserFlags {
  HouseBalance = 1 << 8,
  EarlySupporter = 1 << 9,
  TeamUser = 1 << 10,
  - System = 1 << 12,
  BugHunterLevel2 = 1 << 14,
  VerifiedBot = 1 << 16,
  EarlyVerifiedBotDeveloper = 1 << 17,
  