I get notified by threads that I'm not subscribed to

### Steps to reproduce

1. In a room or a private message, someone else starts a thread on a message I did not send, or replies to a thread that I'm not subscribed to.

### Outcome

#### What did you expect?
Nothing. Life goes on and I keep focusing while others have a conversation in a thread.

#### What happened instead?
The client sees unread messages in the room. It doesn't send a noisy notification, but the room is marked unread until I open the thread and read it. Needless to say, this is very annoying.

### Operating system

macOS

### Browser information

Brave v1.48.164, Chromium 110.0.5481.100

### URL for webapp

app.element.io

### Application version

Element version: 1.11.23

Olm version: 3.2.12

### Homeserver

element.io

### Will you send logs?

Yes

Reproduce the behavior in the Element webapp at app.element.io using the reported room or private-message thread scenario, then trace the client handling of thread subscriptions and unread room state. Done means messages in an unsubscribed thread no longer mark the room unread, while subscribed or relevant messages still do.

Written by the indexing model from the issue text.