Remove unneeded dummy test

This commit removes an unneeded dummy test from
PreBuiltXPackTransportClientTests. The dummy test was needed when the
sole test in the suite was skipped in some configuration. This test is
no longer skipped though so the dummy test can be removed.

Original commit: elastic/x-pack-elasticsearch@9cdfcc3be5

elasticsearch-transport-client/src/test/java/org/elasticsearch/xpack/client/PreBuiltXPackTransportClientTests.java

@@ -20,7 +20,6 @@ import static org.junit.Assert.assertEquals;
  */
 public class PreBuiltXPackTransportClientTests extends RandomizedTest {
 
-    @Test
     public void testPluginInstalled() {
         try (TransportClient client = new PreBuiltXPackTransportClient(Settings.EMPTY)) {
             Settings settings = client.settings();
@@ -28,9 +27,4 @@ public class PreBuiltXPackTransportClientTests extends RandomizedTest {
         }
     }
 
-    // dummy test so that the tests pass on JDK9 as the only test in this module is disabled on JDK9
-    @Test
-    public void testDummy() {
-
-    }
 }