Allow Jira issues without GitLab issues enabled
What does this MR do?
Follow-up from !35273 (comment 371445892).
The latest design, #223787[jira-integration-with-new-section.png] (scroll to the bottom) allows having GitLab issues disabled but Jira issues enabled.
![#223787[jira-integration-with-new-section.png]](https://gitlab.com/gitlab-org/gitlab/-/issues/223787/designs/jira-integration-with-new-section.png){kind=link}
Consider disabling GitLab issues if they won't otherwise be used.
Related to #223916 (closed)
Edited by Arturo Herrero