You can uninstall or removes an installed gsettings-ubuntu-schemas package itself from Ubuntu 16.04 LTS (Xenial Xerus) through the terminal,
$ sudo apt-get remove gsettings-ubuntu-schemas
If you would like to remove gsettings-ubuntu-schemas and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove gsettings-ubuntu-schemas
If you use with purge options to gsettings-ubuntu-schemas package all the configuration and dependent packages will be removed.
$ sudo apt-get purge gsettings-ubuntu-schemas
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove gsettings-ubuntu-schemas