MFH: r441311

Update _KDE_APPLICATIONS_ATTIC_VERSION to 16.12.3 to fix fetching of distfiles

KDE has moved distfiles for applications 16.12.3 to Attic/ on their mirros.

Reported by: Matthias Apitz <guru@unixarea.de>
Reviewed by: rakuco
Approved by: rakuco (mentor, implicit)
Differential Revision: https://reviews.freebsd.org/D10830

Approved by: ports-secteam (blanket), rakuco (mentor)