Merge pull request #8239 from AvaloniaUI/fixes/osx-shadow-invalidation

OSX Shadow invalidation when window sized

native/Avalonia.Native/src/OSX/WindowImpl.mm

@@ -140,6 +140,8 @@ void WindowImpl::BringToFront()
         [Window orderFront:nullptr];
     }
     
+    [Window invalidateShadow];
+    
     for(auto iterator = _children.begin(); iterator != _children.end(); iterator++)
     {
         (*iterator)->BringToFront();