How to Hide the "Disable Full site editing" Admin Menu

function plt_hide_disable_full_site_editing_menus() {
	//Hide the "Tools → Disable Full site editing" menu.
	remove_submenu_page('tools.php', 'disable-fse');
}

add_action('admin_menu', 'plt_hide_disable_full_site_editing_menus', 101);

Where do I put this code?