Fix 404 link: /documentation/references/artifacts/tests

[yada]

Broken link (404)

• URL: https://microcks.io/documentation/references/artifacts/tests
• HTTP status: 404
• Found on: https://microcks.io/documentation/references/artifacts/soapui-conventions/
• Also found on: https://microcks.io/documentation/references/artifacts/soapui-conventions

What to do

• Replace with the correct/current documentation page for tests (or the intended section).
• If the content was renamed or moved, update the link accordingly.

Help needed

If you don’t know the replacement URL, ask in comments and we’ll help find it.

[rissh]

/assign @rissh