unnecessary filter

scripts/copythemecss.js

@@ -1,3 +1,2 @@
 var fs = require('fs-extra');
-var filter = { filter: /\.css$/ };
-fs.copySync('src/theme/index.css', 'example/build/theme.css', filter);
+fs.copySync('src/theme/index.css', 'example/build/theme.css');