Fix compilation on rrf plugin

Author: carlosdelest

x-pack/plugin/rank-rrf/src/internalClusterTest/java/org/elasticsearch/xpack/rank/rrf/RRFRetrieverBuilderIT.java

@@ -764,6 +764,7 @@ public void testRRFFiltersPropagatedToKnnQueryVectorBuilder() {
             new TestQueryVectorBuilderPlugin.TestQueryVectorBuilder(new float[] { 3 }),
             10,
             10,
+            null,
             null
         );
         source.retriever(