Update ORMInvalidArgumentException.php

Author: lacatoire

src/ORMInvalidArgumentException.php

@@ -309,7 +309,7 @@ private static function newEntityFoundThroughRelationshipMessage(array $associat
             . ' configured to cascade persist operations for entity: ' . self::objToStr($entity) . '.'
             . ' To solve this issue: Either explicitly call EntityManager#persist()'
             . ' on this unknown entity or configure cascade persist'
-            . ' this association in the mapping for example #[ORM\ManyToOne(..., cascade: ['persist'])].'
+            . ' this association in the mapping for example #[ORM\ManyToOne(..., cascade: [\'persist\'])].'
             . (method_exists($entity, '__toString')
                 ? ''
                 : ' If you cannot find out which entity causes the problem implement \''