comms/fl{digi,rig}: Fix MASTER_SITES

• Remove upstream site from MASTER_SITES as it seems to drop legacy versions.

Reported by: diizzy@
Reviewed by: db@ (Mentor)
Approved by: yuri@ (Mentor)

Fixes: 01026e48 comms/flrig: Fix and improve the port

Differential Revision: https://reviews.freebsd.org/D52030