cmd/upspin-audit: fix typo in help message
cmd/upspin-audit: fix typo in help message

Change-Id: I1ba97580fb91a6fd44985d864aae589646642caa
Reviewed-on: https://upspin-review.googlesource.com/18360
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

upspin/upspin,upspin/upspin