Remove inheritance on Contao\Controller

[fritzmg]

Currently the following error will occur during contao:migrate:

 [Error]
  Call to protected Contao\System::__construct() from context 'Contao\CoreBundle\Command\MigrateCommand'  


Exception trace:
  at vendor\menatwork\selectmodule\system\modules\selectModule\config\runonce.php:59
 include() at vendor\contao\contao\core-bundle\src\Command\MigrateCommand.php:275

This is because the migration class extends from Contao\Controller and does not provide its own constructor (the parent constructor is protected). Since the migration class does not actually use anything from Contao\Controller (or Contao\System) via its object instance, the inheritance can simply be removed to fix it.