Update forms.rst

Co-authored-by: Antoine Lamirault <[email protected]>

Author: Arkalo2

forms.rst

@@ -952,7 +952,8 @@ Extra fields
 
 All form fields are considered properties of the object but you can inject
 fields directly into your view without specifying them in the form definition.
-They can be retrieved via the ``getExtraData`` :class:`Symfony\\Component\\Form\\FormTypeInterface`.
+They can be retrieved via the :method:`FormInterface::getExtraData() <Symfony\\Component\\Form\\FormInterface::getExtraData>`
+method.
 
 This is a creation user form::