Revert "Point OAuth URLs to Jira connect instance_url"

What does this MR do and why?

Reverts !97310 (merged) because of a bug described here: !97310 (diffs, comment 1095967919)

Screenshots or screen recordings

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.