Fix for delete-unused-accounts-cron example (#996)

Removed .default to resolve TypeError: PromisePool is not a constructor

Author: edward62740

delete-unused-accounts-cron/functions/index.js

@@ -18,7 +18,7 @@
 const functions = require('firebase-functions');
 const admin = require('firebase-admin');
 admin.initializeApp();
-const PromisePool = require('es6-promise-pool').default;
+const PromisePool = require('es6-promise-pool');
 // Maximum concurrent account deletions.
 const MAX_CONCURRENT = 3;