Fix moveBefore feature detection

`moveBefore` was moved to the `ParentNode` mixin as per whatwg/dom#1307 (comment) (and was committed in whatwg/dom@3f3e94c)

As a result, its existence can no longer be checked on `Node.prototype` but must be checked in `Element.prototype`.

packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js

@@ -780,7 +780,7 @@ const supportsMoveBefore =
   // $FlowFixMe[prop-missing]: We're doing the feature detection here.
   enableMoveBefore &&
   typeof window !== 'undefined' &&
-  typeof window.Node.prototype.moveBefore === 'function';
+  typeof window.Element.prototype.moveBefore === 'function';
 
 export function appendChild(
   parentInstance: Instance,