fix(api): exclude s51 attachments from redaction publishing validation (idas-525)

[cprieststephens]

Describe your changes

Issue ticket number and link

IDAS-525: Bug: S51 advice log link not visible on website after CBOS publish

Type of change 🧩

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please explain in the description section above)

Checklist before requesting a review

• I have performed a self-review of my own code
• I have double checked this work does not include any hardcoded secrets or passwords
• I have made corresponding changes to the documentation
• I have provided details on how I have tested my code
• I have referenced the ticket number above
• I have provided a description of the ticket
• I have included unit tests to cover any testable code changes