How to Hide the "Head & Footer Code" Admin Menu

function plt_hide_head_footer_code_menus() {
	//Hide the "Tools → Head & Footer Code" menu.
	remove_submenu_page('tools.php', 'head_footer_code');
}

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

Where do I put this code?