Apply babel to react-intl to remove prop-types (#3914)

config/webpack/loaders/babel.js

@@ -1,6 +1,7 @@
 module.exports = {
   test: /\.js$/,
-  exclude: /node_modules/,
+  // include react-intl because transform-react-remove-prop-types needs to apply to it
+  exclude: /node_modules\/(?!react-intl)/,
   loader: 'babel-loader',
   options: {
     forceEnv: process.env.NODE_ENV || 'development',