How to Hide the "Enable DB Tools" Admin Menu

function plt_hide_enable_database_tools_menus() {
	//Hide the "Settings → Enable DB Tools" menu.
	remove_submenu_page('options-general.php', 'enable-database-tools');
}

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

Where do I put this code?