You can uninstall or removes an installed libgtkhtml-editor-4.0-0 package itself from Ubuntu 14.04 LTS (Trusty Tahr) through the terminal,
$ sudo apt-get remove libgtkhtml-editor-4.0-0
If you would like to remove libgtkhtml-editor-4.0-0 and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove libgtkhtml-editor-4.0-0
If you use with purge options to libgtkhtml-editor-4.0-0 package all the configuration and dependent packages will be removed.
$ sudo apt-get purge libgtkhtml-editor-4.0-0
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 libgtkhtml-editor-4.0-0