remove unused class `MainRequestBuilder` (#70944)

server/src/main/java/org/elasticsearch/action/main/MainRequestBuilder.java

@@ -1,19 +0,0 @@
-/*
- * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
- * or more contributor license agreements. Licensed under the Elastic License
- * 2.0 and the Server Side Public License, v 1; you may not use this file except
- * in compliance with, at your election, the Elastic License 2.0 or the Server
- * Side Public License, v 1.
- */
-
-package org.elasticsearch.action.main;
-
-import org.elasticsearch.action.ActionRequestBuilder;
-import org.elasticsearch.client.ElasticsearchClient;
-
-public class MainRequestBuilder extends ActionRequestBuilder<MainRequest, MainResponse> {
-
-    public MainRequestBuilder(ElasticsearchClient client, MainAction action) {
-        super(client, action, new MainRequest());
-    }
-}