fixing typo in config var

Author: sachin-maheshwari

config/default.js

@@ -22,7 +22,7 @@ module.exports = {
   // We define the time period of the cached token.
   TOKEN_CACHE_TIME: process.env.TOKEN_CACHE_TIME || 86400000,
   AUTH0_CLIENT_ID: process.env.AUTH0_CLIENT_ID,
-  AUTH0_CLIENT_Secret: process.env.AUTH0_CLIENT_SECRET,
+  AUTH0_CLIENT_SECRET: process.env.AUTH0_CLIENT_SECRET,
   SCOPES: {
     'writeBusApi': 'write:bus_api',
     'readBusTopics': 'read:bus_topics'