You can simply turn off that Depricated message and ignore it for now. You would only be forced to update your code when you go to a php7 server... this is just a warning.
To upgrade you just have to install DataBridge 2 and then open any Recordsets, Insert, Update, and Delete Server behaviors on the page and switch them to the MySQLi connection. Once you click OK with a MySQLi connection, then the code is updated to MySQLi.