Remove non-batch async contact/host deletion actions

They have been superseded by DeleteContactsAndHostsAction.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=134424453

java/google/registry/flows/async/DnsRefreshForHostRenameAction.java

@@ -39,6 +39,7 @@ import org.joda.time.DateTime;
 /**
  * Enqueues DNS refreshes for applicable domains following a host rename.
  */
+//TODO(b/26140521): Delete this once non-batched DNS host refresh mapreduce is deleted.
 @Action(path = "/_dr/task/dnsRefreshForHostRename")
 public class DnsRefreshForHostRenameAction implements Runnable {