Name the test more specifically

Author: gmarouli

x-pack/plugin/downsample/src/internalClusterTest/java/org/elasticsearch/xpack/downsample/DownsampleIT.java

@@ -28,7 +28,7 @@
 
 public class DownsampleIT extends DownsamplingIntegTestCase {
 
-    public void testDownsampling() throws Exception {
+    public void testDownsamplingPassthroughDimensions() throws Exception {
         String dataStreamName = "metrics-foo";
 
         putTSDBIndexTemplate("my-template", List.of("metrics-foo"), null, """