You can uninstall or removes an installed gtkmorph-example package itself from Ubuntu 16.04 LTS (Xenial Xerus) through the terminal,
$ sudo apt-get remove gtkmorph-example
If you would like to remove gtkmorph-example and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove gtkmorph-example
If you use with purge options to gtkmorph-example package all the configuration and dependent packages will be removed.
$ sudo apt-get purge gtkmorph-example
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 gtkmorph-example