cmd/cron: fix accidental fmt.Errorf instead of log.Fatalf

Change-Id: Iebc7cae95b4e599a0e264668e364392b125c78ab
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/456234
Reviewed-by: Julie Qiu <julieqiu@google.com>

cmd/cron/main.go

@@ -91,7 +91,7 @@ func main() {
 
 	handlerTimeout, err := strconv.Atoi(timeout)
 	if err != nil {
-		fmt.Errorf("strconv.Atoi(%q): %v", timeout, err)
+		log.Fatalf("strconv.Atoi(%q): %v", timeout, err)
 	}
 	mw := middleware.Timeout(time.Duration(handlerTimeout) * time.Minute)
 	http.Handle("/new/", mw(makeNewVersionsHandler(db, idxClient, *workers)))