try to revert karma change

lib/config/karma.conf-all.js

@@ -76,18 +76,6 @@ module.exports = function (config) {
 
         browsers: ['Chrome'],
 
-        customLaunchers: {
-            ChromeHeadless: {
-                base: 'Chrome',
-                flags: [
-                    '--no-sandbox',
-                    '--headless',
-                    '--disable-gpu',
-                    '--remote-debugging-port=9222'
-              ]
-            }
-        },
-
         // Karma plugins loaded
         plugins: [
             require('../node_modules/karma-jasmine'),