When leaving a call/room in which a project was shared, the shared
project notification was not getting dismissed when the person that
shared the project left the room.
Although there was a `cx.emit(Event::Left)` call inside room, the event
was never received in the `project_shared_notification` module, because
the room is dropped before the event can be dispatched. Moving the
`cx.emit(Event::Left)` to the active call fixed the problem. Also
renamed `Event::Left` to `Event::RoomLeft` because the room join
equivalent is also called `Event::RoomJoined`.


Release Notes:

- Fixed project shared notification staying open, when the user that
shared the project left the room