Remove duplicate var definition as in aspnet#966

Author: SteveSandersonMS

templates/VueSpa/webpack.config.js

@@ -7,7 +7,6 @@ const bundleOutputDir = './wwwroot/dist';
 module.exports = (env) => {
     const isDevBuild = !(env && env.prod);
 
-    const bundleOutputDir = './wwwroot/dist';
     return [{
         stats: { modules: false },
         context: __dirname,