FAL-740 Improve layout and accuracy of django admin docs
This improves the layout (previously was a bugged ordered list) and accuracy (adding extra steps that I needed) of the docs for setting up django admin access for discovery.
*Jira tickets*: (https://openedx.atlassian.net/browse/OSPR-5565)
1. check the rendering of the changed section
[x] edX reviewers TBD
Looks like discovery is with Vanguards now, can your team please review this OSPR?