minor symfony#8439 Update parameters.rst (atailouloute)

This PR was merged into the 2.7 branch.

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Update parameters.rst

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9b03342 Update parameters.rst

Author: wouterj

service_container/parameters.rst

@@ -80,7 +80,6 @@ and hidden with the service definition:
     .. code-block:: php
 
         use AppBundle\Mailer;
-        use Symfony\Component\DependencyInjection\Reference;
 
         $container->setParameter('mailer.transport', 'sendmail');