code: public static void unRegisterMixPush() {
      AVInstallation installation = AVInstallation.getCurrentInstallation();
      String vendor = installation.getString(AVInstallation.VENDOR);
      if (!StringUtil.isEmpty(vendor)) {
        installation.put(AVInstallation.VENDOR, "lc");
        installation.saveInBackground().subscribe(ObserverBuilder.buildSingleObserver(new SaveCallback() {
          @Override
          public void done(AVException e) {
            if (null != e) {
              printErrorLog("unRegisterMixPush error!");
            } else {
              LOGGER.d("Registration canceled successfully!");
            }
          }
        }));
      }
    }
docs: 取消混合推送的注册
  取消成功后，消息会通过 LeanCloud websocket 发送