To uninstall ubuntu-release-upgrader-gtk just follow these instructions.
sudo apt-get remove ubuntu-release-upgrader-gtk
This will remove just the ubuntu-release-upgrader-gtk package itself.
sudo apt-get remove --auto-remove ubuntu-release-upgrader-gtk
This will remove the ubuntu-release-upgrader-gtk package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for ubuntu-release-upgrader-gtk then this will work.
sudo apt-get purge ubuntu-release-upgrader-gtk
Or similarly, like this ubuntu-release-upgrader-gtk
sudo apt-get purge --auto-remove ubuntu-release-upgrader-gtk
|Maintainer||Ubuntu Developers <firstname.lastname@example.org>|
|Description||manage release upgrades|