spec: added a few version references where they were missing

Change-Id: I30ea95f0d2c06d169ca01f5408819af2ed2a8cf3
Reviewed-on: https://go-review.googlesource.com/c/go/+/783363
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>