Add FF defaulted to true scenario to docs

doc/development/changelog.md

@@ -44,8 +44,9 @@ the `author` field. GitLab team members **should not**.
   a changelog entry regardless of these guidelines if the contributor wants one.
   Example: "Fixed a typo on the search results page."
 - Any docs-only changes **should not** have a changelog entry.
-- Any change behind a feature flag **should not** have a changelog entry. The
-  entry should be added [in the merge request removing the feature flags](feature_flags/development.md).
+- Any change behind a feature flag **should not** have a changelog entry - unless
+  the feature flag has been defaulted to true. The entry should be added
+  [in the merge request removing the feature flags](feature_flags/development.md).
   If the change includes a database migration (regular, post, or data migration),
   there should be a changelog entry for the migration change.
 - A fix for a regression introduced and then fixed in the same release (i.e.,