[Documentation] Add instance scope for audit events in documentation

What does this MR do and why?

Added documentation for newly added InstanceScope for instance level audit events.

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.

Related to #418185 (closed)