Add audit event for user unban action

What does this MR do and why?

This MR partially addresses the feature request: #377620 (closed) - logs audit events for the following actions:

• User Unbanned via Admin API
• User Unbanned UI/Admin Area

Screenshots or screen recordings

How to set up and validate locally

1. Check the current behaviour in the master branch
2. Ban and unban a user account and notice that it does not logs the audit event
3. Checkout the feature branch
4. Ban and unban the user and navigate to the Audit events page(http://localhost:3000/admin/audit_logs) and verify the audit event for the unban action.

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.