To uninstall xserver-xephyr just follow these instructions.
sudo apt-get remove xserver-xephyr
This will remove just the xserver-xephyr package itself.
sudo apt-get remove --auto-remove xserver-xephyr
This will remove the xserver-xephyr package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for xserver-xephyr then this will work.
sudo apt-get purge xserver-xephyr
Or similarly, like this xserver-xephyr
sudo apt-get purge --auto-remove xserver-xephyr
|Maintainer||Debian X Strike Force <firstname.lastname@example.org>|
|Description||nested X server much like Xnest. It is based on the kdrive X server, and as a result it supports newer extensions than Xnest, including render and composite.|