Is the project (that you blocked out in red) one of your actual products?
Part of your app maybe using some back-end service of a google cloud account - do a search for the phrase "appspot.com" in your code, which could point to where this is happening.
Yes. I got the same e-mail to an app that is unpublished in the Play Store.
It used Firebase Storage.
I'll remove the project in the Firebase and see if that fix it.