Fixed error with removal of global.Promise override

refs #12182

These were missed in the cleanup and were causing errors.

core/server/services/bulk-email/index.js

@@ -1,4 +1,5 @@
 const _ = require('lodash');
+const Promise = require('bluebird');
 const moment = require('moment-timezone');
 const errors = require('@tryghost/errors');
 const {i18n} = require('../../lib/common');

core/server/services/mega/mega.js

@@ -1,4 +1,5 @@
 const _ = require('lodash');
+const Promise = require('bluebird');
 const debug = require('ghost-ignition').debug('mega');
 const url = require('url');
 const moment = require('moment');