Remove 'unloadable' from bundled sample plugin (#27963).

Patch by Mischa The Evil.


git-svn-id: http://svn.redmine.org/redmine/trunk@17170 e93f8b46-1217-0410-a6f0-8f06a7374b81

extra/sample_plugin/app/controllers/example_controller.rb

@@ -1,7 +1,5 @@
 # Sample plugin controller
 class ExampleController < ApplicationController
-  unloadable
-
   layout 'base'
   before_action :find_project, :authorize
   menu_item :sample_plugin