juvix format removes stuff from markdown files

[lukaszcz]

I ran make format-juvix-files and the markdown typechecking tests got broken as a result.

The misformatted markdown files:

• tests/positive/MarkdownImport/B.juvix.md
• tests/positive/MarkdownImport/C.juvix.md

[paulcadman]

We have an old issue for markdown formatter support (linking it here so we remember to close it when this is fixed):

• Formatter support for Juvix Markdown  #2519