Ask HN: How can I tell Google to let go of an old email address?

I used to have a *13@gmail.com address, two smartphones ago. On my current phone I have been using a completely different account, which is now my primary.

I occasionally get email on the old account, forwarded to my new account, since apparently Google still thinks it is mine, and fair enough. How can I tell them that I don't give a damn about that account, and the other person can have it?