Improve security merge request template

Highlight and explain why that the security issue must be linked to the
release tracking issue. This may help eliminate confusion that assigning
to the release bot is enough.

.gitlab/issue_templates/Security developer workflow.md

@@ -10,10 +10,11 @@ Set the title to: `Description of the original issue`
 
 - [ ] Read the [security process for developers] if you are not familiar with it.
   - Verify if the issue you're working on `gitlab-org/gitlab` is confidential, if it's public fix should be placed on GitLab canonical and no backports are required.
-- [ ] Mark this [issue as linked] to the Security Release Tracking Issue. You can find it on the topic of the `#releases` Slack channel.
+- [ ] **IMPORTANT**: Mark this [issue as linked] to the Security Release Tracking Issue. You can find it on the topic of the `#releases` Slack channel. This issue
+MUST be linked for the release bot to know that the associated merge requests should be merged for this security release.
 - Fill out the [Links section](#links):
   - [ ] Next to **Issue on GitLab**, add a link to the `gitlab-org/gitlab` issue that describes the security vulnerability.
-- [ ] Add one of the `~severity::x` labels to the issue and all associated merge requests. 
+- [ ] Add one of the `~severity::x` labels to the issue and all associated merge requests.
 
 ## Development