cmd/dist: make two related panic messages more consistent
In contrast to the HasSuffix argument, there's no need or benefit in
having a ":" before the "racebench" variant mentioned in the message.
(The variant comes after the colon separator—it doesn't include it.)
Change-Id: Ie9948104de9449422037bf39245944255b98f1b5
Reviewed-on: https://go-review.googlesource.com/c/go/+/497735
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org> Reviewed-by: Austin Clements <austin@google.com>