cmd/upspin-audit: update the package doc comment
cmd/upspin-audit: update the package doc comment

Change-Id: I578695faa31c28ad866b71067d271053957350c8
Reviewed-on: https://upspin-review.googlesource.com/17680
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

upspin/upspin,upspin/upspin