Removed redundant bulk email settings migration

no issue

core/server/data/migrations/versions/3.1/05-add-bulk-email-settings.js

@@ -1,63 +0,0 @@
-const _ = require('lodash');
-const Promise = require('bluebird');
-const common = require('../../../../lib/common');
-
-module.exports.config = {
-    transaction: true
-};
-
-module.exports.up = (options) => {
-    let localOptions = _.merge({
-        context: {internal: true}
-    }, options);
-    const settingsKey = 'members_subscription_settings';
-    return localOptions
-        .transacting('settings')
-        .then((response) => {
-            if (!response) {
-                common.logging.warn('Cannot find settings.');
-                return;
-            }
-            let subscriptionSettingsEntry = response.find((entry) => {
-                return entry.key === settingsKey;
-            });
-
-            if (!subscriptionSettingsEntry) {
-                common.logging.warn('Cannot find members subscription settings.');
-                return;
-            }
-            let subscriptionSettings = JSON.parse(subscriptionSettingsEntry.value);
-
-            let hasMailgunApiKeyProperty = Object.prototype.hasOwnProperty.call(subscriptionSettings, 'mailgunApiKey');
-            let hasMailgunDomainProperty = Object.prototype.hasOwnProperty.call(subscriptionSettings, 'mailgunDomain');
-
-            if (!hasMailgunApiKeyProperty) {
-                subscriptionSettings.mailgunApiKey = '';
-                common.logging.info('Adding mail provider API key to members settings');
-            } else {
-                common.logging.warn('Mail provider API key setting already exists in members settings.');
-            }
-
-            if (!hasMailgunDomainProperty) {
-                subscriptionSettings.mailgunDomain = '';
-                common.logging.info('Adding mailgun domain to members settings');
-            } else {
-                common.logging.warn('Mailgun domain setting already exists in members settings.');
-            }
-
-            return localOptions
-                .transacting('settings')
-                .where('key', settingsKey)
-                .update({
-                    value: JSON.stringify(subscriptionSettings)
-                });
-        });
-};
-
-// `up` only runs in order to normalize new member subscription settings which was added
-// no need for down migration as its non-breaking up migration for future versions only
-module.exports.down = () => Promise.resolve();
-
-module.exports.config = {
-    transaction: true
-};