cmd/dist: remove redundant 'go test -race' call

In CL 207962, I removed a seemingly-redundant -i flag. As it turns
out, the -i flag has *two* meanings: “install dependencies”, and “do
not actually run the test”. Without the flag, we omit the former
behavior, but add the latter.

We're about to run specific tests from these binaries on the very next
line, so don't preemptively run all of the tests.

Updates #30316

Change-Id: Ie3d8a37dc5f6bd98c232b308b0a6a165b5d82f7c
Reviewed-on: https://go-review.googlesource.com/c/go/+/207966


Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>