testing: do not print 'root' benchName during test of package testing
$ cd $GOROOT/src/testing
$ go test
root
root
root
root
PASS
$
The root prints have been happening since Go 1.14.
There is a test in sub_test.go that calls b.Run directly
with a benchmark named "root", which triggers the print.
Silence them.
Change-Id: I2f0c186f04c6139bc24fab0e91975fcf0a8e80fc
Reviewed-on: https://go-review.googlesource.com/c/go/+/421437
Run-TryBot: Russ Cox <rsc@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>