openfact: Allow 6.x

[bastelfreak]

This enables people to test their openvox 8 in CI with openfact 6. openfact 6 will be bundled in openvox 9 packages only.

Short description

Checklist

I have:

• read the CONTRIBUTING.md document
• read and accepted the Developer Certificate of Origin document and added a Signed-off-by annotation to each of my commits
• read and accepted the AI Policy document and added Generated-by or Assisted-by annotations to each of my commits created with the help of an AI agent
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[bastelfreak]

before we merge this, we need to update the vox pupuli tooling to ensure we don't pull in openfact 6 by accident in our unit tests. And it would be great to extend the CI matrix to test on openfact 5 and 6 I guess? And update openvoxserver-ca first, otherwise we cannot pull in openfact 6 anyways.