user_parter removes other users from room when deactivation endpoint is called

This issue has been migrated from [#16582](https://github.com/matrix-org/synapse/issues/16582).

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### Description

Whenever I call the deactivate (+erase) endpoint on synapse (this case for userA) it kept removing another user (userB) from all rooms.
Today this happened for a second user (userC). The notable difference here is that userB had left one of the rooms on their own. C hasn't so far.

### Steps to reproduce

- Deactivate+Erase userA
- Watch public rooms
- See userA unsetting their display name and leaving
- See userB and userC leaving all public rooms they were in

### Homeserver

Selfhostes

### Synapse Version

1.94.0

### Installation Method

Docker (matrixdotorg/synapse)

### Database

single postgres server, no restore from backup

### Workers

Single process

### Platform

Debian 11 with docker

### Configuration

Presence and retention are enabled in the affected public rooms.
The public rooms have a 48h retention policy for about 1.5 years.

The homeserver does not federate.

### Relevant log output

```shell
2023-10-31 09:18:04,843 - synapse.handlers.deactivate_account - 158 - INFO - POST-911131 - Marking @userA:myhomeserver as erased
2023-10-31 09:18:04,845 - synapse.federation.sender - 592 - INFO - process_event_queue_for_federation-1377 - Unexpectedly did not have cached prev group for $oxitnVVee-cjwUyKUZgPf1iHCbQ0kYYvXbov3uoZXyU
2023-10-31 09:18:04,853 - synapse.handlers.deactivate_account - 234 - INFO - user_parter_loop-5 - Starting user parter
2023-10-31 09:18:04,861 - synapse.handlers.deactivate_account - 240 - INFO - user_parter_loop-5 - User parter parting '@userB:myhomeserver'
2023-10-31 09:18:04,873 - synapse.handlers.deactivate_account - 254 - INFO - user_parter_loop-5 - User parter parting '@userB:myhomeserver' from '!wmwqhJvBlcVtlMzYXp:myhomeserver'
2023-10-31 09:18:05,119 - synapse.handlers.deactivate_account - 254 - INFO - user_parter_loop-5 - User parter parting '@userB:myhomeserver' from '!WCxYbgOzUJowbPisiS:myhomeserver'
2023-10-31 09:18:05,127 - synapse.federation.sender - 592 - INFO - process_event_queue_for_federation-1378 - Unexpectedly did not have cached prev group for $S4RKH353eV6CNCxkP3aVVVreIu6qLYmuqZEhwV9fhDE
2023-10-31 09:18:05,338 - synapse.handlers.deactivate_account - 243 - INFO - user_parter_loop-5 - User parter finished parting '@userB:myhomeserver'
2023-10-31 09:18:05,339 - synapse.federation.sender - 592 - INFO - process_event_queue_for_federation-1379 - Unexpectedly did not have cached prev group for $mJL1JXe8swj8vFf0MZLdXvwx4UZxRf1YyAw1Q42L-yw
2023-10-31 09:18:05,343 - synapse.handlers.deactivate_account - 240 - INFO - user_parter_loop-5 - User parter parting '@userC:myhomeserver'
2023-10-31 09:18:05,352 - synapse.handlers.deactivate_account - 254 - INFO - user_parter_loop-5 - User parter parting '@userC:myhomeserver' from '!wmwqhJvBlcVtlMzYXp:myhomeserver'
2023-10-31 09:18:05,553 - synapse.handlers.deactivate_account - 254 - INFO - user_parter_loop-5 - User parter parting '@userC:myhomeserver' from '!WfkDZztWcIEzOOmRNW:myhomeserver'
```

### Anything else that would be useful to know?

_No response_