You can turn off deprecated messages in your php.ini file. The code only needs to be updated if you move to PHP7.
You should be able to adjust the setting in your hosting control panel or php.ini file directly if you have access to it and turn off deprecated messages in the php.ini file like:
error_reporting = E_ALL & ~E_DEPRECATED & ~E_NOTICE
Or you may add the following line to the top of any page that has the message:
error_reporting(E_ALL & ~E_DEPRECATED & ~E_NOTICE);