Update simple-example.rst

Just a little typo, now we use ./styles and not ../css

Author: Yoann-TYT

frontend/encore/simple-example.rst

@@ -17,7 +17,7 @@ application: it will *require* all of the dependencies it needs (e.g. jQuery or
     // assets/app.js
     // ...
 
-    import '../css/app.css';
+    import './styles/app.css';
 
     // var $ = require('jquery');