Make repositories final

Author: Andrey Ershov

server/src/main/java/org/elasticsearch/action/admin/cluster/repositories/get/GetRepositoriesResponse.java

@@ -39,7 +39,7 @@
  */
 public class GetRepositoriesResponse extends ActionResponse implements ToXContentObject {
 
-    private RepositoriesMetaData repositories;
+    private final RepositoriesMetaData repositories;
 
     GetRepositoriesResponse() {
         repositories = new RepositoriesMetaData(Collections.emptyList());