duplicate dashboard id in tidb.json cause UI in mess

[D3Hunter]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

duplicate id include

   2 "id": 315,
   2 "id": 312,
   2 "id": 311,
   2 "id": 309,
   2 "id": 308,

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

master