Don't tag ServerAlert notices as diagnostic

- These notices are intended to be acted upon by the
  front end application, so should not by classified as
  diagnostic.

- ServerAlerts may still be quiesced with EmitServerAlerts.

psiphon/notice.go

@@ -873,7 +873,7 @@ func NoticeServerAlert(alert protocol.AlertRequest) {
 	repetitionKey := fmt.Sprintf("ServerAlert-%+v", alert)
 	outputRepetitiveNotice(
 		repetitionKey, "", 0,
-		"ServerAlert", noticeIsDiagnostic, "reason", alert.Reason, "subject", alert.Subject)
+		"ServerAlert", 0, "reason", alert.Reason, "subject", alert.Subject)
 }
 
 type repetitiveNoticeState struct {