remove backward compatibility variables from flag preprocessor

  // Backward compatibility: The following section preserves some deprecated
  // variables either to make old flag.tpl.php files continue to work, or to
  // prevent PHP from generating E_NOTICEs there. @todo: Remove these sometime.
  $variables['setup'] = FALSE;
  $variables['last_action'] = $variables['status'];

A new major version seems like a good time to remove these!