PHP warning: unregister_setting was called with an argument that is deprecated

Hi there,

I’m currently doing some debugging on my site and when I deactivated this plugin I got several of the following warning message on my debug.log file:

[17-Dec-2018 22:06:57 UTC] PHP Notice: unregister_setting was called with an argument that is <strong>deprecated</strong> since version 4.7.0! <code>$sanitize_callback</code> is deprecated. The callback from <code>register_setting()</code> is used instead. in /path/to/wp-includes/functions.php on line 4080

After inspecting the plugin’s code, I noticed that all calls to unregister_setting() in its deactivation function are referencing different callback functions as the third argument which -as the warning message states- has been deprecated since WordPress 4.7.

While it’s nothing major really, it’d be nice if this could be fixed.

Thanks for the wonderful plugin!