Revert "Mute SpecificMasterNodesIT.testElectOnlyBetweenMasterNodes()"

This reverts commit 2964ceaa0371d8bd1665e599c6395a7e7026d094.

server/src/test/java/org/elasticsearch/cluster/SpecificMasterNodesIT.java

@@ -86,7 +86,6 @@ public class SpecificMasterNodesIT extends ESIntegTestCase {
             .execute().actionGet().getState().nodes().getMasterNode().getName(), equalTo(nextMasterEligibleNodeName));
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/38331")
     public void testElectOnlyBetweenMasterNodes() throws Exception {
         internalCluster().setBootstrapMasterNodeIndex(0);
         logger.info("--> start data node / non master node");