drop Dpkg::MaxArgs in favor of Dpkg::MaxArgsBytes

drop Dpkg::MaxArgs in favor of Dpkg::MaxArgsBytes

We had an old FIXME saying that it is probably pointless to do this if
we limit by length of the commandline already and I completely agree.
The splitting is bad enough if it must be done, so we should only do it
if we have to (as in absolute length of commandline) and, but that is
just a remark, it is unlikely that we ever have/had a call triggering
this as the default value was ~32000 items…