Wrong date-format for timestamp in the generated pdf

### Description of the bug

![Image](https://github.com/user-attachments/assets/13ac6765-665d-40db-807a-c435c4d14b17)

### Related issues
- https://github.com/Altinn/app-frontend-react/issues/3106

### Steps To Reproduce

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### Additional Information

_No response_