CTECH-3305: Add FBN_NEXUS_USERNAME and FBN_NEXUS_PASSWORD to PR tests

[adamMQM]

Pull Request Checklist

• [x] Changes follow the style guide
• [x] Tests pass
• [x] Raised the PR against the develop branch
• [x] Notebook outputs do not contain any priviledged data

Description of the PR

[adamMQM]

/LGTM