update MASTER_SITES to fix distfiles

I noticed this port is currently broken:

BROKEN= no public distfiles

Then I found the public archive at:
https://freedv.com/wp-content/uploads/sites/8/2017/10/codec2-0.7.tar.xz
(the checksum matches)

I think the port can be "fixed" with the attached patch.

Thanks!

Update the LOCAL copy I forgot to add the last time (db)

PR: ports/223163
Submitted by: tj+freebsd_ports@a13.fr