How to Hide the "Maintenance Mode" Admin Menu

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

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

Where do I put this code?