Remove 'new' keyword before Promise.race()

Summary:
I'm not sure if this was actually breaking anything, but I don't think `new` before `Promise.race()` is conventional.
Closes https://github.com/facebook/react-native/pull/9817

Differential Revision: D3836814

Pulled By: javache

fbshipit-source-id: 3bde46dca3760c3f7f3427f6346dd5f16f8ac011

react-packager/src/AssetServer/index.js

@@ -21,7 +21,7 @@ const createTimeoutPromise = (timeout) => new Promise((resolve, reject) => {
 });
 function timeoutableDenodeify(fsFunc, timeout) {
   return function raceWrapper(...args) {
-    return new Promise.race([
+    return Promise.race([
       createTimeoutPromise(timeout),
       Promise.denodeify(fsFunc).apply(this, args)
     ]);