unexpected comment for renaming index in `admin show ddl jobs`

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

``` SQL
mysql> admin show ddl jobs;
+--------+---------+------------+---------------------------------+----------------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+------------+-----------------------------+
| JOB_ID | DB_NAME | TABLE_NAME | JOB_TYPE | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME | START_TIME | END_TIME | STATE | COMMENTS |
+--------+---------+------------+---------------------------------+----------------------+-----------+----------+-----------+----------------------------+----------------------------+----------------------------+------------+-----------------------------+
| 696 | test | tccc6f564 | add index | write reorganization | 2 | 203 | 0 | 2025-04-08 16:26:30.392000 | 2025-04-08 16:26:30.539000 | NULL | cancelling | txn-merge, max_node_count=3 |
| 697 | test | tccc6f564 | add column | none | 2 | 203 | 0 | 2025-04-08 16:26:30.392000 | NULL | NULL | queueing | |
| 698 | test | tccc6f564 | alter table multi-schema change | none | 2 | 203 | 0 | 2025-04-08 16:26:30.394000 | NULL | NULL | queueing | |
| 698 | test | tccc6f564 | add column /* subjob */ | none | 2 | 203 | 0 | 2025-04-08 16:26:30.394000 | NULL | NULL | queueing | |
| 698 | test | tccc6f564 | add column /* subjob */ | none | 2 | 203 | 0 | 2025-04-08 16:26:30.394000 | NULL | NULL | queueing | |
| 698 | test | tccc6f564 | add index /* subjob */ | none | 2 | 203 | 0 | 2025-04-08 16:26:30.394000 | NULL | NULL | queueing | |
| 698 | test | tccc6f564 | add column /* subjob */ | none | 2 | 203 | 0 | 2025-04-08 16:26:30.394000 | NULL | NULL | queueing | |
| 698 | test | tccc6f564 | rename index /* subjob */ | none | 2 | 203 | 0 | 2025-04-08 16:26:30.394000 | NULL | NULL | queueing | max_node_count=3 |
| 702 | test | tccc6f564 | truncate table | none | 2 | 203 | 0 | 2025-04-08 16:26:30.399000 | NULL | NULL | queueing | |
| 703 | test | tccc6f564 | drop column | public | 2 | 203 | 0 | 2025-04-08 16:26:30.407000 | NULL | NULL | queueing | |
| 706 | test | tccc6f564 | truncate table | none | 2 | 203 | 0 | 2025-04-08 16:26:30.429000 | NULL | NULL | queueing | |
| 707 | test | tccc6f564 | add index | none | 2 | 203 | 0 | 2025-04-08 16:26:30.430000 | NULL | NULL | queueing | max_node_count=3 |
| 708 | test | tccc6f564 | add index | none | 2 | 203 | 0 | 2025-04-08 16:26:30.430000 | NULL | NULL | queueing | max_node_count=3 |
| 709 | test | tccc6f564 | add index | none | 2 | 203 | 0 | 2025-04-08 16:26:30.435000 | NULL | NULL | queueing | max_node_count=3 |
| 710 | test | tccc6f564 | modify column | none | 2 | 203 | 0 | 2025-04-08 16:26:30.438000 | NULL | NULL | queueing |
...

```

### 2. What did you expect to see? (Required)
The comment for `rename index` should be empty

### 3. What did you see instead (Required)
| 698 | test | tccc6f564 | rename index /* subjob */ | none | 2 | 203 | 0 | 2025-04-08 16:26:30.394000 | NULL | NULL | queueing | max_node_count=3 |

### 4. What is your TiDB version? (Required)
master