Remove useless test005_todopack test

This test doesn't work because it requires a pack file which we have
lost to the ages.  We couldn't include it because the pack was actually
a copy of the GPL'd C git.git project, and was there to test some sort
of corner case that the test never documented properly.

Change-Id: I282ee1c6a637a8654df93a3847507a6c60e4cfab
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>