cmd/dist: remove chatty log.Print

In CL 206757 I added a log.Printf to identify when GOROOT is not read-only.
However, it interacts badly with test sharding in the builders:
the log is repeated for every shard.

Since the log statement isn't particularly high-value, just remove it.

Updates #30316

Change-Id: I385a7f35da59e38ad8b9beef92dc11af931d9571
Reviewed-on: https://go-review.googlesource.com/c/go/+/206898
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/dist/test.go

@@ -195,7 +195,8 @@ func (t *tester) run() {
 	restoreGOROOT := func() {}
 	if strings.HasPrefix(os.Getenv("GO_BUILDER_NAME"), "linux-") {
 		if os.Getuid() == 0 {
-			log.Printf("Not making GOROOT unwritable: running as root, so permissions would have no effect.")
+			// Don't bother making GOROOT unwritable:
+			// we're running as root, so permissions would have no effect.
 		} else {
 			restoreGOROOT = t.makeGOROOTUnwritable()
 		}