Adjust changelog step on security MR template

The new changelog process has been rolled out. This commit updates the
security release MR template to use this new process instead of
generating a file.

Related to https://gitlab.com/gitlab-com/gl-infra/delivery/-/issues/1767

.gitlab/merge_request_templates/Security Release.md

@@ -16,7 +16,7 @@ See [the general developer security release guidelines](https://gitlab.com/gitla
 - [ ] Merge request targets `master`, or a versioned stable branch (`X-Y-stable-ee`).
 - [ ] Milestone is set for the version this merge request applies to. A closed milestone can be assigned via [quick actions].
 - [ ] Title of this merge request is the same as for all backports.
-- [ ] A [CHANGELOG entry] is added without a `merge_request` value, with `type` set to `security`
+- [ ] A [CHANGELOG entry] has been included, with `Changelog` trailer set to `security`.
 - [ ] For the MR targeting `master`:
   - [ ] Assign to a reviewer and maintainer, per our [Code Review process].
   - [ ] Ensure it's approved according to our [Approval Guidelines].
@@ -37,7 +37,7 @@ See [the general developer security release guidelines](https://gitlab.com/gitla
 
 [GitLab Security]: https://gitlab.com/gitlab-org/security/gitlab
 [quick actions]: https://docs.gitlab.com/ee/user/project/quick_actions.html#quick-actions-for-issues-merge-requests-and-epics
-[CHANGELOG entry]: https://docs.gitlab.com/ee/development/changelog.html
+[CHANGELOG entry]: https://docs.gitlab.com/ee/development/changelog.html#overview
 [Code Review process]: https://docs.gitlab.com/ee/development/code_review.html
 [Approval Guidelines]: https://docs.gitlab.com/ee/development/code_review.html#approval-guidelines
 [Canonical repository]: https://gitlab.com/gitlab-org/gitlab