Fixed bug wrong string concat syntax

Silly me

Author: haphan

src/Compute/v2/Api.php

@@ -683,7 +683,7 @@ public function getQuotaSet(): array
     public function getQuotaSetDetail(): array
     {
         $data = $this->getQuotaSet();
-        $data['path'] += '/detail';
+        $data['path'] .= '/detail';
 
         return $data;
     }