You can uninstall or removes an installed aspell-de package itself from Ubuntu 16.10 (Yakkety Yak) through the terminal,
$ sudo apt-get remove aspell-de
If you would like to remove aspell-de and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove aspell-de
If you use with purge options to aspell-de package all the configuration and dependent packages will be removed.
$ sudo apt-get purge aspell-de
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 aspell-de