Notifications about read messages don't disappear

### Your use case

#### What would you like to do?

I have quite a few rooms with "noisy" notifications on. Most of the time, I'm working on Element Desktop, and I read the messages corresponding to those important notifications here.

When I leave my desk and take my phone, it's full of Element notifications. A few of them are relevant, but they're drowned in irrelevant ones (since I already read those messages on my computer).

Removing notifications for messages I have already read would de-clutter the experience and make notifications much less distracting.

#### Why would you like to do it?

I would like to have only relevant notifications on my phone so I don't spend too much time manually triaging them.

#### How would you like to achieve it?

I would expect iOS to automatically remove the notifications of the messages I have already read (whether it is on the same device or another one) :)

### Have you considered any alternatives?

N/A

### Additional context

N/A

No files, tests, or entry points are identified in the issue. Start by locating Element iOS's notification and read-state handling, then verify that notifications for messages read on either device are removed while unrelated unread notifications remain.

Written by the indexing model from the issue text.