Complement flake `TestClientSpacesSummary/query_whole_graph`

This issue has been migrated from [#16097](https://github.com/matrix-org/synapse/issues/16097).

---

https://github.com/matrix-org/synapse/actions/runs/5817983175/job/15773549259

```
room_hierarchy_test.go:223: MatchResponse JSONCheckOff(rooms): item {"room_id":"!aQzJLviGMWyWBfeqsp:hs1","num_joined_members":1,"world_readable":false,"guest_can_join":false,"children_state":[]} failed checks: room !aQzJLviGMWyWBfeqsp:hs1 got name want R3 - http://127.0.0.1:33483/_matrix/client/v1/rooms/%21oMnYreevZVhiopVBax:hs1/hierarchy => {"rooms":[{"room_id":"!oMnYreevZVhiopVBax:hs1","name":"Root","num_joined_members":1,"join_rule":"public","world_readable":false,"guest_can_join":false,"room_type":"m.space","children_state":[{"type":"m.space.child","state_key":"!jnnhfQsWMJwxebMHdm:hs1","content":{"suggested":true,"via":["hs1"]},"sender":"@alice:hs1","origin_server_ts":1691652214430},{"type":"m.space.child","state_key":"!eCEHifEGNNQzMeafzA:hs1","content":{"via":["hs1"]},"sender":"@alice:hs1","origin_server_ts":1691652214595},{"type":"m.space.child","state_key":"!iLmLtbudHfsxIhuEif:hs1","content":{"suggested":true,"via":["hs1"]},"sender":"@alice:hs1","origin_server_ts":1691652214682}]},{"room_id":"!jnn
hfQsWMJwxebMHdm:hs1","name":"R1","num_joined_members":1,"join_rule":"public","world_readable":false,"guest_can_join":false,"children_state":[]},{"room_id":"!eCEHifEGNNQzMeafzA:hs1","name":"Sub-Space 1","topic":"Some topic for sub-space 1","num_joined_members":1,"join_rule":"public","world_readable":false,"guest_can_join":false,"room_type":"m.space","children_state":[{"type":"m.space.child","state_key":"!pILweHymafrdFGIVLR:hs1","content":{"via":["hs1"]},"sender":"@alice:hs1","origin_server_ts":1691652214929}]},{"room_id":"!pILweHymafrdFGIVLR:hs1","name":"SS2","num_joined_members":1,"join_rule":"public","world_readable":false,"guest_can_join":false,"room_type":"m.space","children_state":[{"type":"m.space.child","state_key":"!aQzJLviGMWyWBfeqsp:hs1","content":{"via":["hs1"]},"sender":"@alice:hs1","origin_server_ts":1691652215011},{"type":"m.space.child","state_key":"!nShMNjYqittEJNtNLk:hs1","content":{"via":["hs1"]},"sender":"@alice:hs1","origin_server_ts":1691652215115}]},{"room_id":"!aQzJLviGMWyWBfeqsp:hs1","n
um_joined_members":1,"world_readable":false,"guest_can_join":false,"children_state":[]},{"room_id":"!nShMNjYqittEJNtNLk:hs1","name":"R4","num_joined_members":1,"join_rule":"public","world_readable":true,"guest_can_join":false,"children_state":[]},{"room_id":"!iLmLtbudHfsxIhuEif:hs1","name":"R2","num_joined_members":1,"join_rule":"public","world_readable":false,"guest_can_join":false,"children_state":[]}]}
```