Update routing.rst

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

Author: MrYamous

routing.rst

@@ -1253,7 +1253,7 @@ automatically converted to their value by Symfony.
 
 .. versionadded:: 6.3
 
-    Using Backed Enum as route parameter is available since Symfony 6.3.
+    Using a `\BackedEnum` as route parameter is available since Symfony 6.3.
 
 .. code-block:: php-attributes