testing: delete unused stopAlarm()

The function call was removed in:
ead08e91

Change-Id: I78fe563c9ea4554811c74130533d2186a65d3033
Reviewed-on: https://go-review.googlesource.com/35532Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/testing/testing.go

@@ -1027,13 +1027,6 @@ func startAlarm() {
 	}
 }
 
-// stopAlarm turns off the alarm.
-func stopAlarm() {
-	if *timeout > 0 {
-		timer.Stop()
-	}
-}
-
 func parseCpuList() {
 	for _, val := range strings.Split(*cpuListStr, ",") {
 		val = strings.TrimSpace(val)