minor #14527 Update simple-example.rst (Yoann-TYT)

This PR was merged into the 5.1 branch.

Discussion
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 Update simple-example.rst

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

Commits
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bdbd7a6 Update simple-example.rst

Author: wouterj

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');