$ sudo apt-get remove prooftree 

Uninstall prooftree including dependent package

If you would like to remove prooftree and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove prooftree 

Use Purging prooftree

If you use with purge options to prooftree package all the configuration and dependent packages will be removed.

$ sudo apt-get purge prooftree 

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 prooftree 

See Also,