Clarify nested dictionaries in lists

What does this MR do?

Clarify how YAML handles nested dictionaries in lists. In my experience, Salt gives no error if the user gets this wrong.

The double Note looks wrong, but I don't know what formatting would be more suitable.

Merge requirements satisfied? (FOR REVIEWER USE ONLY)

• Verify the pipeline is passing
• Check rendered output to ensure formatting is correct for any special directives such as notes, tables, lists, and images
• Review new or modified topics to ensure they follow the style guide
• Review new or modified topics to ensure they follow the Writing Salt documentation (rST guide)