fix: align OpenID4VP request with working ZK example

[rondublin]

⚠️
Hello, and thank you for your contributions!

Please review the following checklist before creating a new pull request:

• Review and contribute to existing pull requests and open issues to avoid redundant efforts.
• Read the contribution guidelines.
• Assign reviewers.
• If applicable, include a reference to related issues.

⚠️ Delete this block before creating the pull request.

Describe the changes proposed
A clear and concise description of the changes included in this pull request.

Screenshots / Videos
If useful, include any screeshots or screencasts to better explain the change.

Additional context
Add any other context about the change here.