Update 'removed assignee' note to include old assignee reference

What does this MR do?

As discussed in the issue #30101 (closed), it adds old assignee reference to removed assignee note message

Are there points in the code the reviewer needs to double check?

Maybe a migration which updates existing note messages on the db should be created? I don't think that old assignee informations are still present after the update action has finished. Maybe they could retrieved anyway?

Why was this MR needed?

In order to solve issue #30101 (closed)

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [-] Documentation created/updated
• [-] API support added
• [-] Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • [-] Has been reviewed by Frontend
  • Has been reviewed by Backend
  • [-] Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #30101 (closed)