remove redundant dockpanel dock.

src/Avalonia.Themes.Default/WindowNotificationManager.xaml

@@ -8,7 +8,7 @@
                     <StackPanel.DataTemplates>
                         <DataTemplate DataType="INotification">
                             <StackPanel Spacing="8" Margin="12">
-                                <TextBlock DockPanel.Dock="Top" Text="{Binding Title}" FontWeight="Medium" />
+                                <TextBlock Text="{Binding Title}" FontWeight="Medium" />
                                 <TextBlock MaxHeight="80" Text="{Binding Message}" TextWrapping="Wrap" Margin="0,0,12,0"/>
                             </StackPanel>
                         </DataTemplate>