Remove main from scheduler index.js

Author: rickhanlonii

packages/scheduler/package.json

@@ -2,7 +2,6 @@
   "name": "scheduler",
   "version": "0.20.1",
   "description": "Cooperative scheduler for the browser environment.",
-  "main": "index.js",
   "repository": {
     "type": "git",
     "url": "https://github.com/facebook/react.git",