[Fix #8320] Replace Gitter with Discord
[Fix #8320] Replace Gitter with Discord

bbatsov/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,tejasbubane/rubocop,maxjacobson/rubocop,bbatsov/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,rrosenblum/rubocop,maxjacobson/rubocop,maxjacobson/rubocop