Convert fc-cache(1) calls in pkg-plist to use @fc keyword
fonts.cache-1 lines started to appear after rP148143 but became
obsolete since fc-cache -s support (i.e. /var/db/fontconfig)
and several FC_CACHE_VERSION bumps.
nReviewed by: hrs
Approved by: portmgr blanket
Approved by: bapt (mentor)