Fix NotificationCard to determine the type of notification from an inherited INotification object

[Onebeld]

What does the pull request do?

Fixed a very small flaw where NotificationCard only defined the notification type from the Notification class, but not from the INotification interface, resulting in the notification type always remaining the default if the object is inherited from the interface.

What is the updated/expected behavior with this PR?

NotificationCard now takes all classes inherited from INotification to define the type of notification.

[Onebeld]

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[avaloniaui-team]

You can test this PR using the following package version. 11.0.999-cibuild0037548-beta. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]