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