Trigger the desired code path

Since v2.7.0 the ORM avoids using extra queries via the paginator
component when maximum results isn't set on the original query. With
that change, this test was not executing the code path that it was
expected to run.

This makes sure we trigger the forcing of custom DBAL types when
hydrating the identifiers, making sure we don't introduce bugs.

More info:
- Forcing DBAL type conversion: doctrine#7905
- Issue on optimisation: doctrine#7829
- PR on optimisation: doctrine#7863
- Minor BC-break docs: https://github.com/doctrine/orm/blob/2.11.x/UPGRADE.md#minor-bc-break-paginator-output-walkers-arent-be-called-anymore-on-sub-queries-for-queries-without-max-results

tests/Doctrine/Tests/ORM/Functional/PaginationTest.php

@@ -670,6 +670,7 @@ public function testCustomIdTypeWithoutOutputWalker(): void
 
         $dql   = 'SELECT p FROM Doctrine\Tests\Models\CustomType\CustomIdObjectTypeParent p';
         $query = $this->_em->createQuery($dql);
+        $query->setMaxResults(1);
 
         $paginator = new Paginator($query, true);
         $paginator->setUseOutputWalkers(false);