fix webpack config

webpack.config.prod.js

@@ -45,10 +45,6 @@ module.exports = {
       date: buildDate,
       version: pkgJson.version
     }),
-    new HtmlWebpackPlugin({
-      inject: true,
-      template: path.join(__dirname, 'src/migrate.html')
-    }),
     new ExtractTextPlugin({
       filename: '[hash:6].css',
       disable: false,