Add warning about CI traces when enabling S3

What does this MR do?

Traces may go missing when they're saved in the builds folder and moved to the local artifacts folder in HA set ups.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content