Review docs for "Support automatic transitions of Jira issues, and disabling transitions"

References

Merged MR that introduced documentation requiring review: !55773 (merged)

Related issue(s): #322477 (closed), #16119 (closed)

Further Details

• Some of the changes were already reviewed in !53760 (merged), which was reverted in !54807 (merged).
• The frontend has two links to this page at https://gitlab.com/gitlab-org/gitlab/-/blob/d480e2974ca7d7fdc8074c4735e2621d2a0bf672/app/assets/javascripts/integrations/edit/components/jira_trigger_fields.vue#L33-54, if we change headings the code needs to be synchronized.
• The whole page could use a clean-up 😅