fix(sharding): typo in addOrderBy

Signed-off-by: Benjamin Gaussorgues <benjamin.gaussorgues@nextcloud.com>

lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php

@@ -277,7 +277,7 @@ public function setFirstResult($firstResult) {
 
 	public function addOrderBy($sort, $order = null) {
 		$this->registerOrder((string)$sort, (string)$order ?? 'ASC');
-		return parent::orderBy($sort, $order);
+		return parent::addOrderBy($sort, $order);
 	}
 
 	public function orderBy($sort, $order = null) {