Added missing tilda (yml config)

Loïc Chardonnet · weaverryan · commit d715a649ec49 · 2013-09-18T10:18:40.000-05:00
The tilda was missing for the YAML configuration.
diff --git a/reference/constraints/Country.rst b/reference/constraints/Country.rst
@@ -24,7 +24,7 @@ Basic Usage
         Acme\UserBundle\Entity\User:
             properties:
                 country:
-                    - Country:
+                    - Country: ~
 
     .. code-block:: php-annotations
 
