appNotification: Fix account removal on quit

Application::prepare-shutdown is emitted when the window is destroyed,
after all its children has been destroyed as well - any signal connected
to an AppNotification has been disconnected by then, so even if we called
close as intended it wouldn't have any effect. So to get the intended
behavior, run close() when the notification is destroyed without being
closed before.
1 job for wip/fmuellner/fix-close-on-quit in 3 minutes and 34 seconds
Status Name Job ID Coverage
passed build-polari #1035