How to Hide the "WEN Maintenance Mode" Admin Menu

function plt_hide_wen_maintenance_mode_menus() {
	//Hide the "Settings → WEN Maintenance Mode" menu.
	remove_submenu_page('options-general.php', 'wen-maintenance-mode');
}

add_action('admin_menu', 'plt_hide_wen_maintenance_mode_menus', 11);

Where do I put this code?