cmd/upspin: delete pointless test in share
cmd/upspin: delete pointless test in share

Found after review of previous CL.

Change-Id: Iaa413b4dc98f01c9dddd5afd3a6385fcd987f632
Reviewed-on: https://upspin-review.googlesource.com/7844
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@google.com>

upspin/upspin,upspin/upspin