Internal links to imported notes can be multiline

### Expected
Internal link should not include line breaks

### Observed
Found thanks to [this bug ](https://github.com/Automattic/simplenote-electron/issues/2646). The exported notes have extra line breaks. Once these notes are imported again, the internal link for the note will include the line break:

### Reproduced
1. Have one note with a single line break between title and content
2. Export it
3. Import it back (no matter if json or plain text)
4. In the other note, type `[` and the note title ~> you will see new line symbols shown in the popup
5. Once entered, the internal link will be placed on multiple lines, and will not be handled correctly in MD view.

### Where did you see the bug
- System Make: Parallels Desktop + MBP 16"
- OS: Windows 10 Home | Ubuntu 20.04 | macOS 11.2.3
- Simplenote app version: 2.8.0-beta2 Desktop

Start by following the reproduction steps for exporting and re-importing a note, then inspect the import/export flow and the internal-link title autocomplete. Done means imported note titles do not show line breaks in the popup, inserted internal links stay on one line, and they render correctly in Markdown view.

Written by the indexing model from the issue text.