Simplify desktop notification checks (#195)
    
    This is the best option I can come up with to deal with #195.
    Update notifications seem to have become transient in KDE lately
    (even in F31 and F32, if I'm looking at these screenshots right).
    This actually simplifies things a lot to do more or less the
    same in the KDE and GNOME paths: open the 'permanent' store of
    notifications (in GNOME you get to it by clicking on the clock,
    in KDE via the systray) and then look for no notifications (live
    path) or only an update notification (post-install path). We
    only run this test for composes so we shouldn't need to worry
    about anything older than F32, and I believe this should work
    for KDE in F32 and F33. I left out click_unwanted_notifications
    for now as I'm hoping it should be unnecessary, but we can add
    it back in if necessary.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>