Drop the dependency on desktop-notification-daemon
    
    We've gotten numerous complaints from users over this dependency, as it
    tends to pull in a random desktop environment (e.g. cinnamon) when doing
    an initial install that includes libnotify in the transaction set.
    
    Furthermore, it would also pull in a full desktop environment to any
    koji builds that include libnotify.
    
    This commit drop the dep to avoid this surprising behaviour.