docs: Translate tests readme update

[romanc]

Description

Markdown error fixes, formatting updates, and minor rewording of the document.

How Has This Been Tested?

I used VSCode's markdown preview to look at the rendered markdown.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas: N/A
• I have made corresponding changes to the documentation
• My changes generate no new warnings: N/A
• Any dependent changes have been merged and published in downstream modules: N/A
• New check tests, if applicable, are included: N/A

[FlorianDeconinck]

LGTM.

We need pyFV3 and ndsl to cross ref each other on the subject in future docs