Fixing for mars/create-react-app-buildpack#156

Author: gdgkirkley

package.json

@@ -14,8 +14,7 @@
     "start": "react-scripts start -p $PORT",
     "build": "react-scripts build",
     "test": "react-scripts test",
-    "eject": "react-scripts eject",
-    "heroku-postbuild": "react-scripts build"
+    "eject": "react-scripts eject"
   },
   "eslintConfig": {
     "extends": "react-app"