Resolve "FF cleanup validate_release_with_author"

What does this MR do and why?

FF is successfully rolledout and default enabled from 15.8 so removing it.

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 #390050 (closed)