default config: remove DHCP, VPN

default config: remove DHCP, VPN

VPN was removed because it pointed to vpnc, which hasn’t been updated
since 2008 and is long obsolete in favor of openconnect. Since different
people use different VPN solutions, though (and other modules configured
by default do actually work regardless of the system), let’s remove this
and have people who need it configure it explicitly.

DHCP was removed because modern systems often don’t use dhclient anymore
(but rather systemd-networkd’s DHCP client, which can also be used via
NetworkManager these days) and because it fails our philosophy test:
it’s not something which you would look at every now and then if
i3status didn’t expose it.