fix: replicas and primary nullable

Author: kai687

specs/search/common/schemas/listIndicesResponse.yml

@@ -48,9 +48,13 @@ fetchedIndex:
       description: A boolean which says whether the index has pending tasks. This value is deprecated and should not be used.
     primary:
       type: string
+      nullable: true
+      default: null
       description: Only present if the index is a replica. Contains the name of the related primary index.
     replicas:
       type: array
+      nullable: true
+      default: null
       items:
         type: string
       description: Only present if the index is a primary index with replicas. Contains the names of all linked replicas.