minor #7552 Update without_class.rst (Benjamin-Porquet)

This PR was submitted for the 3.2 branch but it was merged into the 2.7 branch instead (closes #7552).

Discussion
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Update without_class.rst

A right bracket is missing

Commits
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7082f42 Update without_class.rst

Author: xabbuh

form/without_class.rst

@@ -101,7 +101,7 @@ but here's a short example:
     If you are using validation groups, you need to either reference the
     ``Default`` group when creating the form, or set the correct group on
     the constraint you are adding.
+    
+    .. code-block:: php
 
-.. code-block:: php
-
-    new NotBlank(array('groups' => array('create', 'update'))
+        new NotBlank(array('groups' => array('create', 'update')))