Downgrade changelog editing to warning

What does this MR do and why?

Downgrade changelog editing to warning

For situations like gitlab-org/gitlab#331794 it is necessary to edit the changelog to archive old major versions.

With the current compliance settings it will not be possible to merge gitlab-org/gitlab!109672 (merged)

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.