How to Hide the "Timthumb Scanner" Admin Menu

function plt_hide_timthumb_vulnerability_scanner_menus() {
	//Hide the "Tools → Timthumb Scanner" menu.
	remove_submenu_page('tools.php', 'cg-timthumb-scanner');
}

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

Where do I put this code?