How to Hide the "Disable Gutenberg" Admin Menu

function plt_hide_disable_gutenberg_menus() {
	//Hide the "Settings → Disable Gutenberg" menu.
	remove_submenu_page('options-general.php', 'disable-gutenberg');
}

add_action('admin_menu', 'plt_hide_disable_gutenberg_menus', 1000);

Where do I put this code?