[FLINK-36111][minor][pipeline-connector/paimon] Improve MultiTableCom…

…mittableChannelComputer Topology name

This closes #3559

flink-cdc-connect/flink-cdc-pipeline-connectors/flink-cdc-pipeline-connector-paimon/src/main/java/org/apache/flink/cdc/connectors/paimon/sink/v2/MultiTableCommittableChannelComputer.java

@@ -56,4 +56,9 @@ public int channel(CommittableMessage<MultiTableCommittable> committableMessage)
             return Math.floorMod(Objects.hash(committableMessage), numChannels);
         }
     }
+
+    @Override
+    public String toString() {
+        return "shuffle by table";
+    }
 }