Update when a changelog is required for a feature flag

What does this MR do and why?

Update when a changelog is required for a feature flag

• I think having the word Removing doesn't take into account when a user is keeping the feature flag, but defaulting it on Changing it to Modifying eludes to this nuance

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.