cmd/dist: update to assume Go 1.17.13 as minimal Go bootstrap version

cmd/dist: update to assume Go 1.17.13 as minimal Go bootstrap version

Replace explicit Go version names where possible with generic reference
to Go bootstrap version.

Updates #44505

Change-Id: I4a6439576efd40e72acd26fcc1472a1a8b0b06e7
Reviewed-on: https://go-review.googlesource.com/c/go/+/344330
Auto-Submit: Martin Möhrmann <martin@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>