[arch-dev-public] Dropping fprint

I am dropping fprint_demo, libfprint and pam_fprint from extra, as they are essentially dead projects, and nobody cares about them anyway (libfprint has been out of date for years, I don't even think it got flagged until recently). At the time I added them, I was hoping for them to become active projects that would actually be used by other software, which never happened.