Dashes and list elements are deleted even with Markdown off

It looks like we delete list-starting elements like `-` and `*` whenever the Enter key is pressed and no matter if Markdown is on or off. This can cause some confusion and resulted on a user report.

### Expected
To be able to add a series of empty elements just like I can with the web app:

```
-
-
-
```

On GitHub, for example, we only remove empty list elements (`-` or `*`) if they are followed by an empty space and the `enter` button.

### Observed

We remove `-` and `*` elements even when Markdown is off:

https://user-images.githubusercontent.com/1136160/105849470-335c2080-5fbf-11eb-9da0-495c69ce1f51.mov

### Reproduced

1. Open a note
2. Make sure that Markdown is off
3. Add `-` or `*`
4. Hit `Enter`

User report: 3655526-zen

Make|Model|macOS Version|App Version
-|-|-|-
Mac|MBP 13|Catalina 10.15.7|2.5

Reproduce the issue by opening a note with Markdown off, entering `-` or `*`, and pressing Enter. Compare the behavior with Markdown enabled and with the expected repeated empty elements; done means list markers are not removed when Markdown is off, while the documented empty-list behavior remains correct.

Written by the indexing model from the issue text.