Update OAuth2 token info API docs to be clearer

What does this MR do?

Closes #207064 (closed)

Updates the Token Info API docs to be clearer and more consistent, after suggestions in !21173 (merged).

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content