cmd/go/internal/mvs: omit modules at version "none" in BuildList and Req

For #37438

Change-Id: Icb28035ae4027aa09d8959d4ac2f4b94a6c843a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/266339


Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Bryan C. Mills <bcmills@google.com>