unpack-objects: remove stale and confusing comment
unpack-objects: remove stale and confusing comment

The very initial version of unpack-objects.c::unpack_all() used
to unpack from the end of the pack, but since end of June last
year it was changed to stream from the front and the comment
does not reflect the reality anymore.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git