On GitHub you can add a website URL to the details of a repository. This URL then will get display in the sidebar on the right hand side.

Apparently, Vercel automatically fills in this field when it's empty and you’ve made a production deployment. You can manually empty it, but it will get filled in the next time again.
I don't want it. I want this URL to stay empty.
I didn't find any setting in Vercel to disable this feature. How can I disable it?