update JSXV4 spec

Author: mununki

docs/JSXV4.md

@@ -358,7 +358,7 @@ function has the name of the enclosing module/file.
 // is transformed to
 
 // v4
-React.createElement(React.fragment, {children: [comp1, comp2, comp3]})
+React.createElementVariadic(React.fragment, {}, [comp1, comp2, comp3])
 
 // v4 @ new jsx transform
 React.jsxs(React.jsxFragment, {children: [comp1, comp2, comp3]})