Fabric: Removed declaration of ShadowNode::clearSourceNode()

Summary: This is a leftover from the ealy days of Fabric. The mehtod does not have implementation counterpart and any usage.

Reviewed By: JoshuaGross

Differential Revision: D14402636

fbshipit-source-id: aa2e919084ae7382d3a62af761e1f6eac334fc75

ReactCommon/fabric/core/shadownode/ShadowNode.h

@@ -116,7 +116,6 @@ class ShadowNode : public virtual Sealable,
       const SharedShadowNode &oldChild,
       const SharedShadowNode &newChild,
       int suggestedIndex = -1);
-  void clearSourceNode();
 
   /*
    * Sets local data assosiated with the node.