Updating a note removes the title

When I use `hackmd-cli notes update --noteId="XYZ" --content="New content"` to set the contents of a note, the title of the note is removed. Trying to include the title of the note in the content, e.g.

```
hackmd-cli notes update --noteId="XYZ" --content="# My title\nNew content"
```

does not solve the issue: instead, the `# My title` part is included in the content of the note and the title is still empty.