fixes(Visuals): Suppress warning CS0618 'IVisualWithRoundRectClip' is obsolete: 'Internal API, will be removed in future versions, you've been warned'

src/Avalonia.Visuals/Rendering/ImmediateRenderer.cs

@@ -289,11 +289,14 @@ namespace Avalonia.Rendering
 
                 using (context.PushPostTransform(m))
                 using (context.PushOpacity(opacity))
-                using (clipToBounds 
-                    ? visual is IVisualWithRoundRectClip roundClipVisual 
+                using (clipToBounds
+#pragma warning disable CS0618 // Type or member is obsolete
+                    ? visual is IVisualWithRoundRectClip roundClipVisual
                         ? context.PushClip(new RoundedRect(bounds, roundClipVisual.ClipToBoundsRadius))
                         : context.PushClip(bounds) 
                     : default(DrawingContext.PushedState))
+#pragma warning restore CS0618 // Type or member is obsolete
+
                 using (visual.Clip != null ? context.PushGeometryClip(visual.Clip) : default(DrawingContext.PushedState))
                 using (visual.OpacityMask != null ? context.PushOpacityMask(visual.OpacityMask, bounds) : default(DrawingContext.PushedState))
                 using (context.PushTransformContainer())

src/Avalonia.Visuals/Rendering/SceneGraph/SceneBuilder.cs

@@ -164,10 +164,12 @@ namespace Avalonia.Rendering.SceneGraph
             var visual = node.Visual;
             var opacity = visual.Opacity;
             var clipToBounds = visual.ClipToBounds;
+#pragma warning disable CS0618 // Type or member is obsolete
             var clipToBoundsRadius = visual is IVisualWithRoundRectClip roundRectClip ?
                 roundRectClip.ClipToBoundsRadius :
                 default;
-            
+#pragma warning restore CS0618 // Type or member is obsolete
+
             var bounds = new Rect(visual.Bounds.Size);
             var contextImpl = (DeferredDrawingContextImpl)context.PlatformImpl;