Fix compile error after merge

Author: felixbarny

x-pack/plugin/otel-data/src/test/java/org/elasticsearch/xpack/oteldata/otlp/docbuilder/MetricDocumentBuilderTests.java

@@ -211,7 +211,7 @@ public void testSummary() throws Exception {
             null,
             List.of(),
             "",
-            "metrics-generic.otel-default"
+            TargetIndex.defaultMetrics()
         );
         dataPointGroup.addDataPoint(
             Set.of(),