Do not remove "dead" domains in tootctl accounts cull (#9108)

Leave `tootctl accounts cull` to simply check removed accounts from
live domains, and skip temporarily unavailable domains, while listing
them in the final output for further action.

Add `tootctl domains purge DOMAIN` to be able to purge a domain from
that list manually

lib/mastodon/settings_cli.rb

@@ -9,6 +9,7 @@ module Mastodon
     def self.exit_on_failure?
       true
     end
+
     desc 'open', 'Open registrations'
     def open
       Setting.open_registrations = true