Modify delete post diff response format (#13761)

* Modify delete post diff response format

Updated the delete operation response to return JSON content.

* fix: timestamp open api schema

public/openapi/write/posts/pid/diffs/timestamp.yaml

@@ -19,7 +19,9 @@ delete:
       description: a valid UNIX timestamp
       example: 1611850000000
   responses:
-    '200':
+    "200":
       description: Post diff successfully deleted
       content:
-        $ref: ../diffs.yaml#/get/responses/200/content
+        application/json:
+          schema:
+            $ref: ../diffs.yaml#/get/responses/200/content