Remove useless maybeAddDefaultLoggingJavaOpts from TezClientUtils

After TEZ-3918, which removed most of the method body, only a null check can be found.

  static void maybeAddDefaultLoggingJavaOpts(String logLevel, List<String> vargs) {
    Objects.requireNonNull(vargs);
    TezClientUtils.addLog4jSystemProperties(logLevel, vargs);
  }

I believe this method should be removed and Objects.requireNonNull should be moved to addLog4jSystemProperties