Upgrade `test` version of `pypy`

[scbedd]

Right now we are running pypy3.9. That's still our support python version matrix so there isn't a real urgency to upgrade.

HOWEVER, pypy3.9 is fairly "old" at this point. We should upgrade to a newer version. If we want to stick to older versions of pypy, we should just move to pypy310. If we want to avoid dealing with this for a while, we'll just go straight to pypy311.

@lmazuel do you have an opinion as to which I choose?