SW: drop wvdial from GRML_FULL

SW: drop wvdial from GRML_FULL

The wvdial package was orphaned in 2018 (see
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=901879) and my
assumption is that Point-to-Point protocols aren't really relevant for
Grml users anymore nowadays. It was requested in 2012 (see commit
9c06220097) for GRML_FULL, but if someone really cares about this in
2021 as well it's time to find out (and then we should discuss whether
it's also relevant for GRML_SMALL?).

Removing wvdial package and its dependencies frees ~2.710 kB of disk space.