Core Update 166: Drop old 2007 Pakfire key, and remove it from existing installations

Core Update 166: Drop old 2007 Pakfire key, and remove it from existing installations

It is not necessary to have this key present on IPFire systems anymore,
since it has not been in use for years, and we can expect systems to be
sufficiently up-to-date, so they no longer need to rely on old updates
or add-ons signed with this key.

Also, given the current key was generated in 2018, we should consider a
Pakfire key rollover soon.

Signed-off-by: Peter Müller <peter.mueller@ipfire.org>
Acked-by: Michael Tremer <michael.tremer@ipfire.org>