Mute FullClusterRestartIT#testClosedIndices (#39600)

Relates #39576

Author: DaveCTurner

qa/full-cluster-restart/src/test/java/org/elasticsearch/upgrades/FullClusterRestartIT.java

@@ -960,6 +960,7 @@ public void testSoftDeletes() throws Exception {
      * This test creates an index in the old cluster and then closes it. When the cluster is fully restarted in a newer version,
      * it verifies that the index exists and is replicated if the old version supports replication.
      */
+    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/39576")
     public void testClosedIndices() throws Exception {
         if (isRunningAgainstOldCluster()) {
             createIndex(index, Settings.builder()