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