Prevent bundling aggregations for state events

We're trying this out on hotfixes to see whether it helps address
performance issues. There's no need to do aggregation bundling for
state events anyways.

synapse/rest/admin/rooms.py

@@ -685,7 +685,10 @@ class RoomEventContextServlet(RestServlet):
             results["events_after"], time_now
         )
         results["state"] = await self._event_serializer.serialize_events(
-            results["state"], time_now
+            results["state"],
+            time_now,
+            # No need to bundle aggregations for state events
+            bundle_aggregations=False,
         )
 
         return 200, results