Drop setuptools as a runtime dependency

Because of the change from using setuptools.pkg_resources to using
importlib, we no longer need a runtime dependency on setuptools. It is
still required, however, for running setup.py.

certbot-ci/setup.py

@@ -22,7 +22,6 @@ install_requires = [
     # requests unvendored its dependencies in version 2.16.0 and this code relies on that for
     # calling `urllib3.disable_warnings`.
     'requests>=2.16.0',
-    'setuptools',
     'types-python-dateutil',
 ]