Update controller.rst

Co-authored-by: Oskar Stark <oskarstark@googlemail.com>

Author: dbu

controller.rst

@@ -506,9 +506,9 @@ payload formats::
 
     If you write a JSON API, make sure to declare your route to use the JSON
     format. This will make the error handling output a JSON response in case of
-    validation errors, rather than an HTML page.
+    validation errors, rather than an HTML page::
     
-    ``#[Route('/dashboard', name: 'dashboard', format: 'json')]
+        #[Route('/dashboard', name: 'dashboard', format: 'json')]
 
 Make sure to install `phpstan/phpdoc-parser`_ and `phpdocumentor/type-resolver`_
 if you want to map a nested array of specific DTOs::