People: Relationship codes should count Holdings too

https://muscat.rism.info/admin/people/51041018
This person is linked in the holdings but it says "There are no sources with relator codes."

<img width="439" height="150" alt="Image" src="https://github.com/user-attachments/assets/4a834296-5542-46a2-857f-cfc01a6b5276" />

The list should include holdings as well.