Remove "ForcedLayer" from Sky

sky/engine/core/rendering/RenderLayerModelObject.h

Index: sky/engine/core/rendering/RenderLayerModelObject.h
diff --git a/sky/engine/core/rendering/RenderLayerModelObject.h b/sky/engine/core/rendering/RenderLayerModelObject.h
index d388620f5816d0f81ee5ab96785b5faee650c935..db5108bfd2617c71a8b26239c40db65d8c9ddbf9 100644
--- a/sky/engine/core/rendering/RenderLayerModelObject.h
+++ b/sky/engine/core/rendering/RenderLayerModelObject.h
@@ -32,10 +32,9 @@ class RenderLayer;
 enum LayerType {
     NoLayer,
     NormalLayer,
-    // A forced or overflow clip layer is required for bookkeeping purposes,
+    // An overflow clip layer is required for bookkeeping purposes,
     // but does not force a layer to be self painting.
     OverflowClipLayer,
-    ForcedLayer
 };
 
 class RenderLayerModelObject : public RenderObject {