Do not vendor cookbooks using Berkshelf anymore

Instead, use the Berkshelf support in knife-solo and the
vagrant-berkshelf plugin on Vagrant

cookbooks/mediawiki/Thorfile

@@ -1,12 +0,0 @@
-# encoding: utf-8
-
-require 'bundler'
-require 'bundler/setup'
-require 'berkshelf/thor'
-
-begin
-  require 'kitchen/thor_tasks'
-  Kitchen::ThorTasks.new
-rescue LoadError
-  puts ">>>>> Kitchen gem not loaded, omitting tasks" unless ENV['CI']
-end