Tb 129+ deal with removal of MozElements.NotificationBox.shown()

[RealRaven2000]

the NotificationBox.shown() method gets removed after Thunderbird 128:

https://searchfox.org/mozilla-esr128/source/toolkit/content/widgets/notificationbox.js#339

we used it for finding out older versions of Thunderbird (78 and upwards) which will now fail into the wrong code branch and cause broken notification boxes:

[RealRaven2000]

Fixed in 6.8.1, published on 30/11/2024