Mute CCR retention test that is consistently failing locally and in CI

Author: mark-vieira

x-pack/plugin/ccr/src/test/java/org/elasticsearch/xpack/ccr/CcrRetentionLeaseIT.java

@@ -467,6 +467,7 @@ public void testUnfollowRemovesRetentionLeases() throws Exception {
         }
     }
 
+    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/39201")
     public void testUnfollowFailsToRemoveRetentionLeases() throws Exception {
         final String leaderIndex = "leader";
         final String followerIndex = "follower";