test_egg_fetcher: use newer setuptools on Python 3.10
test_egg_fetcher: use newer setuptools on Python 3.10

setuptools==49.0.0 appears to be the first version compatible with
Python 3.10 -- earlier versions either misdetect the minor version
or try to import MutableMapping from collections which dropped its
deprecated aliases to Collections Abstract Base Classes (bpo-37324).

pytest-dev/pytest-runner