PyPy 3.8+3.9 Migration

We have begun rolling out packages built for PyPy3.8 and PyPy3.9. This work may take a few weeks. See pypy in the user docs for information on how to set up a PyPy environment. Please report issues to the PyPy developers at https://foss.heptapod.net/pypy/pypy. We are also dropping PyPy3.7 in each feedstock as the newer versions of PyPy are added. New versions of migrated feedstocks will not be built for PyPy3.7 and that version of the python interpreter will not be receiving updates. As usual, you can track the status of the migration on our status page.