ksmserver: Fix memory management of notification
Cleanup of notifications happens automatically when they are closed.
There is a fallback timer here that uses the state to check if it should perform additional cleanup.
This is not safe as if we ever had two notifications within 5 seconds we could be in the state WaitingForKnotify but still have the first notification active at this point.
We can let KNotification autodelete continue to take care of it.