Add details to disabled rubocop

What does this MR do and why?

Marshal.load can be a very dangerous method and we have a call where the rubocop rule Security/MarshalLoad is disabled. This was done a long time ago and we were wondering why. I added a link to the discussion so the next person asking themselves this question doesn't have to do the analysis again.

This MR only adds 2 lines of comment and doesn't change any code.

Screenshots or screen recordings

N/A

How to set up and validate locally

Nothing to validate, this only adds a comment

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.