lang/fpc-units: Set VLC unit as a non-default option

Due to the VLC included in KDE, the fpc-units metapackage package coexist
with the KDE metapackage due to FPC's VLC unit requiring QT5.

Until such time where they can coexist, the FPC VLC unit will not be an
on-by-default option to remove this install conflict.

PR: 212919
Reported by: Ian Goddard (bz at austonley.org.uk)