remove unused code

app/mithril/src/server/config/defaults/webpack.config.js

@@ -1,7 +0,0 @@
-import deprecate from 'util-deprecate';
-import { createDefaultWebpackConfig } from '@storybook/core/server';
-
-module.exports = deprecate(
-  createDefaultWebpackConfig,
-  "importing default webpack config generator from '@storybook/mithril/dist/server/config/defaults/webpack.config.js' is deprecated. Use third argument of your exported function instead. See https://storybook.js.org/configurations/custom-webpack-config/#full-control-mode--default"
-);

app/mithril/src/server/iframe.html.ejs

@@ -5,10 +5,6 @@
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <meta content="IE=edge" http-equiv="X-UA-Compatible" />
     <base target="_parent">
-    <script>
-        if (window.parent !== window) {
-        }
-    </script>
     <title>Storybook</title>
     <%= htmlWebpackPlugin.options.data.previewHead %>
 </head>