FIX wrong require path

patches/workload_init.patch

@@ -4,7 +4,7 @@
  
  require 'redmine'
  require File.expand_path('lib/redmine_workload', __dir__)
-+require './group_workload_preparer.rb'
++require './lib/redmine_workload/group_workload_preparer.rb'
  
  Redmine::Plugin.register :redmine_workload do
    name 'Redmine workload plugin'