Remove compiler feature detection for = delete

sky/engine/core/rendering/RenderBlock.h

Index: sky/engine/core/rendering/RenderBlock.h
diff --git a/sky/engine/core/rendering/RenderBlock.h b/sky/engine/core/rendering/RenderBlock.h
index dd64bd5d104108057e47bd1ab216ed50b1b49dc1..d8c4b50406469d28b32e181cec94d2c06b9e85c0 100644
--- a/sky/engine/core/rendering/RenderBlock.h
+++ b/sky/engine/core/rendering/RenderBlock.h
@@ -66,8 +66,8 @@ public:
     RenderObject* lastChild() const { ASSERT(children() == virtualChildren()); return children()->lastChild(); }
 
     // If you have a RenderBlock, use firstChild or lastChild instead.
-    void slowFirstChild() const WTF_DELETED_FUNCTION;
-    void slowLastChild() const WTF_DELETED_FUNCTION;
+    void slowFirstChild() const = delete;
+    void slowLastChild() const = delete;
 
     const RenderObjectChildList* children() const { return &m_children; }
     RenderObjectChildList* children() { return &m_children; }