Unmute SpecificMasterNodesIT test (#44436)

The underlying issue is closed and the fix in #42454 seems to have been
backported to 7.x and 7.3 so we can reactivate the test.

Author: Christoph Büscher

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

@@ -84,7 +84,6 @@ public void testSimpleOnlyMasterNodeElection() throws IOException {
             .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");