Update doctrine.rst

Replace fetchAll() by fetchAllAssociative() method.

Author: jordanjix

reference/configuration/doctrine.rst

@@ -158,7 +158,7 @@ you can access it using the ``getConnection()`` method and the name of the conne
         public function someMethod(ManagerRegistry $doctrine)
         {
             $connection = $doctrine->getConnection('customer');
-            $result = $connection->fetchAll('SELECT name FROM customer');
+            $result = $connection->fetchAllAssociative('SELECT name FROM customer');
 
             // ...
         }