Source

File: wp-includes/ms-deprecated.php

function wpmu_admin_redirect_add_updated_param( $url = '' ) {
	_deprecated_function( __FUNCTION__, '3.3.0', 'add_query_arg()' );

	if ( strpos( $url, 'updated=true' ) === false ) {
		if ( strpos( $url, '?' ) === false )
			return $url . '?updated=true';
		else
			return $url . '&updated=true';
	}
	return $url;
}