admin: fix new document category

src/Bundle/ChillDocStoreBundle/Repository/DocumentCategoryRepository.php

@@ -61,15 +61,4 @@ class DocumentCategoryRepository implements ObjectRepository
     {
         return DocumentCategory::class;
     }
-
-    public function nextIdInsideBundle()
-    {
-        $array_res = $this->em
-            ->createQuery(
-                'SELECT MAX(c.idInsideBundle) + 1 FROM ChillDocStoreBundle:DocumentCategory c'
-            )
-            ->getSingleResult();
-
-        return reset($array_res);
-    }
 }