[ZendBundle] removed obsolete alias

src/Symfony/Bundle/ZendBundle/Resources/config/logger.xml

@@ -37,7 +37,5 @@
         <service id="zend.logger.filter" class="Zend\Log\Filter\Priority">
             <argument>%zend.logger.priority%</argument>
         </service>
-
-        <service id="logger.debug" alias="zend.logger.writer.debug" />
     </services>
 </container>