Invalid implementation of MSC3890

[t3chguy]

While no local_notification_settings event exists for the current device, or a local_notification_settings event exists where is_silenced is falsy, events should be processed as normal and trigger system notifications and sounds where necessary.

Says to treat no event or no is_silenced as if it were false, we default to true: https://github.com/matrix-org/matrix-react-sdk/blob/develop/src/utils/notifications.ts#L54

The wrong unstable prefix is used also org.matrix.msc3890.local_notification_settings vs https://github.com/matrix-org/matrix-spec-proposals/blob/60695654956019c51f88f0f88ca02280ef00bc13/proposals/3890-remote-local-notification-toggle.md#unstable-prefix

[germain-gg]

The rendered link in the MSC does not point to the latest commit. The implementation is correct.

Will fix the default behaviour. I parsed that wrong