fix wrong method name

src/renderers/shared/reconciler/ReactMultiChild.js

@@ -315,7 +315,7 @@ var ReactMultiChild = {
         ReactChildReconciler.unmountChildren(prevChildren);
         for (var name in prevChildren) {
           if (prevChildren.hasOwnProperty(name)) {
-            this._unmountChildByName(prevChildren[name], name);
+            this._unmountChild(prevChildren[name]);
           }
         }
         this.setMarkup(nextMarkup);