You can uninstall or removes an installed libgps21 package itself from Debian 8 (Jessie) through the terminal,
$ sudo apt-get remove libgps21
If you would like to remove libgps21 and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove libgps21
If you use with purge options to libgps21 package all the configuration and dependent packages will be removed.
$ sudo apt-get purge libgps21
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 libgps21