fix(@schematics/angular): sync karma conf template

The `rootUrl` property was added in 73f57f3

Author: cexbrayat

packages/schematics/angular/config/files/karma.conf.js.template

@@ -4,6 +4,7 @@
 module.exports = function (config) {
   config.set({
     basePath: '',
+    rootUrl: '/',
     frameworks: ['jasmine'<% if (needDevkitPlugin) { %>, '@angular-devkit/build-angular'<% } %>],
     plugins: [
       require('karma-jasmine'),