Use translator interface instead of final class

Symfony use a different class when in dev mode and prod mode.

Prod loads `Symfony\Bundle\FrameworkBundle\Translation\Translator`.
Dev loads `Symfony\Component\Translation\DataCollectorTranslator` to gather information for the debug bar.

Fix #1585

src/Wallabag/CoreBundle/Repository/EntryRepository.php

@@ -255,7 +255,7 @@ class EntryRepository extends EntityRepository
      *
      * @param int $userId
      *
-     * @return integer
+     * @return int
      */
     public function countAllEntriesByUsername($userId)
     {