fetch_pack(): drop unused parameters

fetch_pack(): drop unused parameters

We don't need the caller of fetch_pack() to pass in "dest", which is the
remote URL. Since ba227857d2 (Reduce the number of connects when
fetching, 2008-02-04), the caller is responsible for calling
git_connect() itself, and our "dest" parameter is unused.

That commit also started passing us the resulting "conn" child_process
from git_connect(). But likewise, we do not need do anything with it.
The descriptors in "fd" are enough for us, and the caller is responsible
for cleaning up "conn".

We can just drop both parameters.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>