Fix (bug #1862): Do not clear entity manager for doctrine orm populator (#1995)

Bug: #1862
Clear specific entities is deprecated and will not be supported in Doctrine 3.0. (doctrine/orm@9ccb883)
Bug introduced: c49cd54
Related issue: https://stackoverflow.com/questions/18215975/doctrine-a-new-entity-was-found-through-the-relationship

Author: jlekowski

Diff for: src/Faker/ORM/Doctrine/Populator.php

@@ -98,11 +98,9 @@ public function execute($entityManager = null)
                 );
                 if (count($insertedEntities) % $this->batchSize === 0) {
                     $entityManager->flush();
-                    $entityManager->clear($class);
                 }
             }
             $entityManager->flush();
-            $entityManager->clear($class);
         }
 
         return $insertedEntities;