Updating notes does not update all lines

First of all, thanks for maintaining this tool.

Sometimes, when using the `notes update` command, the note is not fully updated. Here is a fairly small example/reproduction:

````sh
$ hackmd-cli notes create --content='
aa

```
aab
```

aab'
ID Title User path Team path
────────────────────── ──────── ───────── ─────────
59bbDYGPSESuaJuBh_fD4A Untitled gitmd
````
to create a note with some content. Now, update it with some other content:
````
$ hackmd-cli notes update --noteId 59bbDYGPSESuaJuBh_fD4A --content='
aa

```json
aabc
```

aabc'
````
However, the last modification (the last line) is not taken into account:
````
$ hackmd-cli export --noteId 59bbDYGPSESuaJuBh_fD4A

aa

```json
aabc
```

aab
````

If I do the `hackmd-cli notes update` command again, the content of the note matches what is required.
However, I've seen some old content/new content pairs where `hackmd-cli notes update` does nothing...

This seems to be a hackmd API bug (rather than the CLI), as I tried to directly write the HTTP requests, and it fails. But I could not find any github repository where we can file issues on the API itself. Feel free to redirect me if I'm not opening the issue in the right repo!

(while writing the HTTP requests by hand, I've also seen a case where writing a newline at the end of the JSON payload would change the outcome of the "update" API request... if that helps to track the bug)

Start by reproducing the issue with the `hackmd-cli notes create`, `hackmd-cli notes update`, and `hackmd-cli export` commands using the content pairs in this report. Compare the exported note after one and two updates, and determine whether the CLI can address the inconsistent HackMD API response; done means the final line is updated reliably.

Escrita pelo modelo de indexação a partir do texto da issue.