Maintenance: Remove obsolete dev script for message bird.

script/messagebird.rb

@@ -1,6 +0,0 @@
-# Copyright (C) 2012-2021 Zammad Foundation, http://zammad-foundation.org/
-
-require 'messagebird'
-
-client = MessageBird::Client.new('OSR2zUFd14Nd5snb8zmEQYoBx')
-client.message_create('Zammad GmbH', '+4917670333748', 'This is a test messageNEW', reference: 'Foobar')