[Cookbook] Fix XML example of RTE

Author: dunglas

cookbook/doctrine/resolve_target_entity.rst

@@ -136,7 +136,7 @@ about the replacement:
             <doctrine:config>
                 <doctrine:orm>
                     <!-- ... -->
-                    <doctrine:resolve-target-entity interface="Acme\InvoiceBundle\Model\InvoiceSubjectInterface">Acme\AppBundle\Entity\Customer</resolve-target-entity>
+                    <doctrine:resolve-target-entity interface="Acme\InvoiceBundle\Model\InvoiceSubjectInterface">Acme\AppBundle\Entity\Customer</doctrine:resolve-target-entity>
                 </doctrine:orm>
             </doctrine:config>
         </container>