[Docs] REST high-level client: Fix code for most basic search request (#28916)

We also need to add the query to the request.

client/rest-high-level/src/test/java/org/elasticsearch/client/documentation/SearchDocumentationIT.java

@@ -129,6 +129,7 @@ public class SearchDocumentationIT extends ESRestHighLevelClientTestCase {
             SearchRequest searchRequest = new SearchRequest(); // <1>
             SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder(); // <2>
             searchSourceBuilder.query(QueryBuilders.matchAllQuery()); // <3>
+            searchRequest.source(searchSourceBuilder); // <4>
             // end::search-request-basic
         }
         {

docs/java-rest/high-level/search/search.asciidoc

@@ -18,6 +18,7 @@ include-tagged::{doc-tests}/SearchDocumentationIT.java[search-request-basic]
 <1> Creates the `SeachRequest`. Without arguments this runs against all indices.
 <2> Most search parameters are added to the `SearchSourceBuilder`. It offers setters for everything that goes into the search request body.
 <3> Add a `match_all` query to the `SearchSourceBuilder`.
+<4> Add the `SearchSourceBuilder` to the `SeachRequest`.
 
 ===== Optional arguments