Add m.room.create as an expected event type to stripped state

We added m.room.create as one of the state event types to return by default in
matrix-org#9448 in order to allow inspecting
the 'type' of a room (which is stored in the create event) without first needing
to join a room.

tests/federation/transport/test_knocking.py

@@ -133,6 +133,16 @@ def send_example_state_events_to_room(
                 )
             )
 
+        # Finally, we expect to see the m.room.create event of the room as part of the
+        # stripped state. We don't need to inject this event though.
+        room_state[EventTypes.Create] = {
+            "content": {
+                "creator": sender,
+                "room_version": RoomVersions.MSC2403.identifier,
+            },
+            "state_key": "",
+        }
+
         return room_state
 
     def check_knock_room_state_against_room_state(