Add praefect section to troubleshooting doc

What does this Merge Request do?

Adds a Praefect section to the troubleshooting doc that has been identified by a few people.

Merge Request checklist

• [-] Tests added for new functionality. If not, please raise Issue to follow-up.
• This change is backward compatible. If not, please include steps to communicate to our users.
• Documentation added/updated, if needed.
• [-] gdk doctor test added, if needed.