minor #19461 Replace fetchAll() by fetchAllAssociative() method (jordanjix)

This PR was submitted for the 6.4 branch but it was merged into the 5.4 branch instead.

Discussion
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Replace `fetchAll()` by `fetchAllAssociative()` method

Replace fetchAll() by fetchAllAssociative() method.

Commits
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3af1d26 Update doctrine.rst

Author: OskarStark

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');
 
             // ...
         }