DOC: vos convertROtoRW security requirements

DOC: vos convertROtoRW security requirements

They were copied from another command; corrected them.

Change-Id: Ic77f1a91520ec4147e42864438d98942f6a7effc
Reviewed-on: http://gerrit.openafs.org/7305
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementix.org>