cmd/dist: remove special test timeout scale for Windows

In https://golang.org/cl/33804 I screwed up a GOOS == "windows"
check into a bogus comparison against GOARCH == "windows".

But turns out the builders are happy anyway, so remove the windows
special case.

Change-Id: I820b1d49d5b3e8cbffe4516fc39f514326dc39f8
Reviewed-on: https://go-review.googlesource.com/33893
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/dist/test.go

@@ -153,7 +153,7 @@ func (t *tester) run() {
 
 	t.timeoutScale = 1
 	switch t.goarch {
-	case "arm", "windows":
+	case "arm":
 		t.timeoutScale = 2
 	case "mips", "mipsle", "mips64", "mips64le":
 		t.timeoutScale = 4