Remove Non DUO Chat explain vulnerability code

What does this MR do and why?

Remove Non DUO Chat explain vulnerability feature, as it has been replaced by a DUO Chat tool.

Issue: #464315 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

⚠ Required Manual Check from a member of the TI team @darbyfrey @dpisek @sming-gitlab ⚠

• Copy the checklist from this issue: FF Cleanup Manual Test Checklist (#478761 - closed)
• Paste the items as a comment in this MR
• Complete all the manual checks