Skip warnings when there are no artifacts skipped for deletion

What does this MR do and why?

We found out from #346261 (comment 1026734304) that we still log warnings even though there were no artifacts skipped for deletion, thus leading to confusion.

This MR addresses this issue and only logs warnings when there were skipped artifacts. Added specs to ensure this.

I did not add a changelog here because this is not a user facing change and just changes logging behavior.

Screenshots or screen recordings

These are strongly recommended to assist reviewers and reduce the time to merge your change.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.