Now that the 'notification tab' on the old layout is no longer available, old installations are stuck with it enabled

### Steps to reproduce

1. Enable the notification tab from Settings -> Lab on an old version of Element Android
2. Upgrade to latest version
3. Try disabling notification tab

### Outcome

#### What did you expect?
With notification tab removed from lab, users who have it enabled should probably be given a way to disable it, or have it disabled for them. I prefer the former (if there's a special command to toggle it on and off that's fine too if it's documented)

#### What happened instead?
Old installations have the notification tab enabled, new installations can't enable it - so my two phones have an inconsistent look and feel.

### Your phone model

Samsung S22

### Operating system version

Android

### Application version and app store

Element version 1.5.10, olm version 3.2.12 from Play Store

### Homeserver

Element One

### Will you send logs?

No

### Are you willing to provide a PR?

No