Updating a shared note result in an error

If we try to update a note that is not ours, but that we are allowed to edit, the note is edited but the API answers with a `403 Forbidden` answer:

```
$ hackmd-cli export --noteId jmYbFyeLQOyS2mwonYqCYw
aa
$ hackmd-cli notes update --noteId jmYbFyeLQOyS2mwonYqCYw --content="bb"
Update note content failed
Error: Received an error response (403 Forbidden) from HackMD
Code: 403
$ hackmd-cli export --noteId jmYbFyeLQOyS2mwonYqCYw
bb
```

This problem is on the hackmd API side, but I don't know on which repo to open the issue...

針對使用者可以編輯的共用筆記，使用 `hackmd-cli export` 和 `hackmd-cli notes update` 重現該流程。接著追蹤筆記更新命令及其 HackMD API 回應處理；當允許的更新不再回報 403，或確認該問題應歸入 HackMD API repository 時，即表示完成。

由索引模型根據 Issue 內容生成。