Fix some redundant serializer declarations

ONOS-6482

Change-Id: I1870a94a3e38f1b820344ff3b2c4abaa239482b5
diff --git a/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java b/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
index 031c805..0575fd3 100644
--- a/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
+++ b/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
@@ -115,7 +115,7 @@
 
     protected KryoNamespace.Builder kryo = new KryoNamespace.Builder()
             .register(URI.class).register(HashSet.class)
-            .register(DeviceId.class).register(PortNumber.class)
+            .register(PortNumber.class)
             .register(NeighborSet.class).register(PolicyGroupIdentifier.class)
             .register(PolicyGroupParams.class)
             .register(GroupBucketIdentifier.class)