Review trestle website links and make sure all are operational

[degenaro]

Describe the bug

Some links may links to other sites, e.g. NIST OSCAL, may not be working, e.g. due to relocation.

To Reproduce

Check external links. If all are working, then there is nothing to do. Otherwise, fix or remove broken links.

Expected behavior

All links should work.

Screenshots / Logs.

N/A

Environment

N/A