Transition ID section should include help text

Problem

As a GitLab user setting up the Jira integration for the first time, there isn't any information related to Transition IDs. More context can be seen here: #16119 (closed)

Proposal

As a smaller step in the right direction, while waiting for #16119 (closed), adding help text around what the feature does and how to set it up should be an easy win.

See Designs section.

Copy:

Jira workflows transitions

Set transition IDs for Jira workflow transition. Learn how to obtaining your transition IDs.