Fix typing

Author: rmpel

src/Base/RestAPI/Controllers/BaseController.php

@@ -119,7 +119,7 @@ protected function defaultTaxonomyParamIsValid(WP_REST_Request $request, string
         return true;
     }
 
-    protected function getOrderClause(mixed $orderBy, mixed $order)
+    protected function getOrderClause(string $orderBy, string $order): array
     {
         $orderArray = [];
         $orderByParts = explode(',', $orderBy);