ReplicationIT: Enable task deletion when testing delete branch

When deletion of tasks is disabled, the test fails because the
previous task for replication of the branch creation is still
persisted. This causes the actual number of tasks to differ from
the expected.

Re-enable deletion for this test only.

Change-Id: I52f58e9f61fbc5f751139c4c11e04ad850b772a3
diff --git a/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationIT.java b/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationIT.java
index ed95f92..d607d86 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/replication/ReplicationIT.java
@@ -328,6 +328,8 @@
   }
 
   private void replicateBranchDeletion(boolean mirror) throws Exception {
+    tasksStorage.disableDeleteForTesting(false);
+
     setReplicationDestination("foo", "replica", ALL_PROJECTS, mirror);
     reloadConfig();