fix example partitioner (#373)

Summary:
Pull Request resolved: #373

also miss from D49171496

Reviewed By: mcr229

Differential Revision: D49325488

fbshipit-source-id: 64da3a4934b2cb561f5ff7b65673f1bd532afceb

Author: cccclai

examples/example_quantizer_and_delegate/example_partitioner.py

@@ -80,7 +80,8 @@ def _partition_graph_module(
                 partition_tags[delegation_tag] = self.delegation_spec
 
         for _, submodule, _ in get_control_flow_submodules(edge_graph_module):
-            self._partition_graph_module(submodule)
+            submodule_partition_tags = self._partition_graph_module(submodule)
+            partition_tags.update(submodule_partition_tags)
 
         return partition_tags