Revert "Mute MinimumMasterNodesIT.testThreeNodesNoMasterBlock()"

This reverts commit 448fc8444559be3145e4a7f65dec794ebbff7b81.

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

@@ -202,7 +202,6 @@ public class MinimumMasterNodesIT extends ESIntegTestCase {
         }
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/39172")
     public void testThreeNodesNoMasterBlock() throws Exception {
         internalCluster().setBootstrapMasterNodeIndex(2);