Remove explicit reference to Microsoft.Windows.CSWinRT #219

Great, so we can remove this now that we aren't using the PrivateAssets="All" workaround from before. Still, this PR is just adding conditions, so we don't include wasdk/winui3 assets under the new Notifications component over in Labs.

I guess we just remove the line entirely then?

Originally posted by @Arlodotexe in #217 (comment)