Changing a user's power level can result in your own power level being lowered

### Steps to reproduce

I tried to lower a problematic user's power level as follows:
1. click on their profile picture
2. select "Custom level" in the "Power level" dropdown
3. unrelated bug: try to enter -1, but the input does not accept `-`, so I either entered 0 or left the field blank
4. press enter
5. an `m.room.power_levels` event is sent, adding an entry for the user with level 0, and changing the entry for the own user from 100 to 50

For future reference:

event `$eOIZHbZLm0g4eCm1WGMQ47qrLfkweOzhmkAyY2D9FQ0` in `!H55QZaxP7zgghhx48z:computer.surgery`

```
{
"type": "m.room.power_levels",
"sender": "@xiretza:xiretza.xyz",
"content": {
"events": {
"im.vector.modular.widgets": 50,
"m.reaction": 0,
"m.room.avatar": 50,
"m.room.canonical_alias": 50,
"m.room.encryption": 100,
"m.room.history_visibility": 50,
"m.room.name": 50,
"m.room.pinned_events": 50,
"m.room.power_levels": 50,
"m.room.redaction": 0,
"m.room.server_acl": 50,
"m.room.tombstone": 100,
"m.room.topic": 50,
"m.space.child": 50
},
"users": {
"@amanda:graven.dev": 50,
"@benjamin:computer.surgery": 50,
"@charles:computer.surgery": 100,
"@erikj:jki.re": 50,
"@jplatte:flipdot.org": 100,
"@jplatte:matrix.org": 0,
"@levans:safaradeg.net": 50,
"@ruma_mod:flipdot.org": 50,
"@tanriol:matrix.org": 50,
"@tanriol:mozilla.org": 50,
"@timokoesters:fachschaften.org": 50,
"@xiretza:xiretza.xyz": 50,
"@thedarkknightx:matrix.org": 0
}
},
"state_key": "",
"origin_server_ts": 1676208005679,
"unsigned": {
"replaces_state": "$dkAAOyNp-a9Fk7OHsi78O3tladXAQ1r8p32HnetUnRU",
"prev_content": {
"events": {
"im.vector.modular.widgets": 50,
"m.reaction": 0,
"m.room.avatar": 50,
"m.room.canonical_alias": 50,
"m.room.encryption": 100,
"m.room.history_visibility": 50,
"m.room.name": 50,
"m.room.pinned_events": 50,
"m.room.power_levels": 50,
"m.room.redaction": 0,
"m.room.server_acl": 50,
"m.room.tombstone": 100,
"m.room.topic": 50,
"m.space.child": 50
},
"users": {
"@amanda:graven.dev": 50,
"@benjamin:computer.surgery": 50,
"@charles:computer.surgery": 100,
"@erikj:jki.re": 50,
"@jplatte:flipdot.org": 100,
"@jplatte:matrix.org": 0,
"@levans:safaradeg.net": 50,
"@ruma_mod:flipdot.org": 50,
"@tanriol:matrix.org": 50,
"@tanriol:mozilla.org": 50,
"@timokoesters:fachschaften.org": 50,
"@xiretza:xiretza.xyz": 100
}
},
"prev_sender": "@jplatte:flipdot.org",
"age": 3147
},
"event_id": "$eOIZHbZLm0g4eCm1WGMQ47qrLfkweOzhmkAyY2D9FQ0",
"room_id": "!H55QZaxP7zgghhx48z:computer.surgery"
}
```

### Outcome

#### What did you expect?

Changing another user's power level does not demote me from Admin to Moderator.

#### What happened instead?

I think the latest change to `m.room.power_levels` before this happened may have been my promotion from `50` to `100`, so maybe that was undone for some reason?

### Operating system

Arch Linux

### Application version

Element version: 1.11.20, Olm version: 3.2.12

### How did you install the app?

_No response_

### Homeserver

_No response_

### Will you send logs?

Yes