Docs: Reveting a feature flag must have a changelog entry as well

We don’t control if users enable a feature flag on their instance, so
for maximum visibility/transparency it’s good to have a changelog in
those cases.

doc/development/changelog.md

@@ -57,7 +57,7 @@ the `author` field. GitLab team members **should not**.
 - Any change behind a feature flag that is **enabled** by default **should** have a changelog entry.
 - Any change that adds new usage data metrics and changes that needs to be documented in Product Intelligence [Event Dictionary](https://about.gitlab.com/handbook/product/product-intelligence-guide/#event-dictionary) **should** have a changelog entry.
 - A change that adds snowplow events **should** have a changelog entry -
-- A change that [removes a feature flag](feature_flags/index.md) **must** have a changelog entry.
+- A change that [removes a feature flag, or removes a feature and its feature flag](feature_flags/index.md) **must** have a changelog entry.
 - A fix for a regression introduced and then fixed in the same release (i.e.,
   fixing a bug introduced during a monthly release candidate) **should not**
   have a changelog entry.