Fixes babel-plugin-react-intl configuration

According to https://www.npmjs.com/package/babel-plugin-react-intl
moduleSourceName is used to indicate the name of react-intl package.

This commit removes configuration value ("./redux-form-validators")
which prevents babel-plugin-react-intl plugin from finding where
react-intl package is and does not generate "./i18n/extracted-messages"
folder from "npm run build" command.

Change-Id: I0481c50199fef8d9719a68e18383a709a493ab9a
Closes-Bug: #1737577

.babelrc

@@ -1,6 +1,13 @@
 {
   "presets": ["es2015", "stage-0", "react"],
   "plugins": [
+    [
+      "react-intl",
+      {
+        "messagesDir": "./i18n/extracted-messages/",
+        "enforceDescriptions": false
+      }
+    ],
     [
       "react-intl",
       {