Adjust Cagra Index degree to fit the default performance of

Elasticsearch

Author: mayya-sharipova

x-pack/plugin/gpu/src/main/java/org/elasticsearch/xpack/gpu/codec/GPUToHNSWVectorsWriter.java

@@ -263,6 +263,7 @@ private String buildGPUIndex(VectorSimilarityFunction similarityFunction, Datase
         // TODO: expose cagra index params of intermediate graph degree, graph degree, algorithm, NNDescentNumIterations
         CagraIndexParams params = new CagraIndexParams.Builder().withNumWriterThreads(1) // TODO: how many CPU threads we can use?
             .withCagraGraphBuildAlgo(CagraIndexParams.CagraGraphBuildAlgo.NN_DESCENT)
+            .withGraphDegree(16)
             .withMetric(distanceType)
             .build();