fix ssr dev config

Author: yyx990803

build/webpack.ssr.dev.config.js

@@ -4,7 +4,6 @@ var alias = require('./alias')
 module.exports = {
   target: 'node',
   entry: path.resolve(__dirname, 'webpack.ssr.dev.entry.js'),
-  target: 'node',
   output: {
     path: path.resolve(__dirname, '../packages/vue-server-renderer'),
     filename: 'create-renderer.js',