Remove elastic.co related link docs

[harold-wang]

Remove elastic.co related link docs in RestHighLevelClient.java and others.

/**
* Asynchronously deletes a document by id using the Delete API.
* See Delete API on elastic.co
* @param deleteRequest the request
* @param options the request options (e.g. headers), use {@link RequestOptions#DEFAULT} if nothing needs to be customized
* @param listener the listener to be notified upon request completion
* @return cancellable that may be used to cancel the request
*/
public final Cancellable deleteAsync(DeleteRequest deleteRequest, RequestOptions options, ActionListener listener) {
return performRequestAsyncAndParseEntity(deleteRequest, RequestConverters::delete, options, DeleteResponse::fromXContent, listener,
Collections.singleton(404));
}

[harold-wang]

The effort to update the Elastic Co URL link will be paused until we new document is available to replace it.

[harold-wang]

#586 has the fix.