Removed unnecessary border

src/PixiEditor.AvaloniaUI/Views/Layers/LayersManager.axaml

@@ -142,7 +142,7 @@
                 IsVisible="{Binding Path=DataContext.ActiveDocument, ElementName=layersManager, Converter={converters1:NotNullToVisibilityConverter}}"
                 Background="{DynamicResource ThemeBackgroundBrush}"
                 Grid.Row="3" VerticalAlignment="Bottom"/>
-            <TreeView DockPanel.Dock="Top" Name="treeView"
+            <TreeView DockPanel.Dock="Top" Name="treeView" BorderThickness="0"
                       ItemsSource="{Binding DataContext.ActiveDocument.StructureRoot.Children, ElementName=layersManager}">
                 <TreeView.ItemsPanel>
                     <ItemsPanelTemplate>