cmd/go/internal/work: add missing newline to go version note

cmd/go/internal/work: add missing newline to go version note

A missed newline was added for one case in CL 162957, but
the parallel no-output case was missed.

Add the missed newline for the second case and update the test to
cover the full line for both cases.

Updates #30263

Change-Id: I02aa523290295a6d409cd68066b45c6990e6fb6e
Reviewed-on: https://go-review.googlesource.com/c/go/+/258758
Reviewed-by: Jay Conrod <jayconrod@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Bryan C. Mills <bcmills@google.com>