Some further ESLint cleanup, remove some unnecessary scripts and lines (#2984)

webpack.config.performance.test.js

@@ -1,10 +1,6 @@
 // Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
-// This file uses CommonJS.
-/* eslint-disable import/no-commonjs */
-'use strict';
-
 const glob = require('glob');
 const {merge} = require('webpack-merge');
 
@@ -15,5 +11,3 @@ module.exports = merge(test, {
         e2e: glob.sync('./e2e/performance/**/*.test.js'),
     },
 });
-
-/* eslint-enable import/no-commonjs */