[PURIFY] remove all trace of x-pack async-search (opensearch-project#10)

This commit removes all trace of Elastic licensed asyc-search

Signed-off-by: Peter Nied <petern@amazon.com>

Author: nknize

client/rest-high-level/src/main/java/org/elasticsearch/client/AsyncSearchClient.java

@@ -271,7 +271,6 @@ public class RestHighLevelClient implements Closeable {
     private final RollupClient rollupClient = new RollupClient(this);
     private final CcrClient ccrClient = new CcrClient(this);
     private final TransformClient transformClient = new TransformClient(this);
-    private final AsyncSearchClient asyncSearchClient = new AsyncSearchClient(this);
 
     /**
      * Creates a {@link RestHighLevelClient} given the low level {@link RestClientBuilder} that allows to build the
@@ -442,16 +441,6 @@ public IndexLifecycleClient indexLifecycle() {
         return ilmClient;
     }
 
-    /**
-     * A wrapper for the {@link RestHighLevelClient} that provides methods for accessing the Elastic Index Async Search APIs.
-     * <p>
-     * See the <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/async-search.html"> X-Pack APIs on elastic.co</a>
-     * for more information.
-     */
-    public AsyncSearchClient asyncSearch() {
-        return asyncSearchClient;
-    }
-
     /**
      * Provides methods for accessing the Elastic Licensed Migration APIs that
      * are shipped with the default distribution of Elasticsearch. All of