Merge pull request readthedocs#5450 from stsewd/update-setuptools

Update version of setuptools

Author: ericholscher

readthedocs/doc_builder/python_environments.py

@@ -284,7 +284,7 @@ def install_core_requirements(self):
             self.project.get_feature_value(
                 Feature.USE_SETUPTOOLS_LATEST,
                 positive='setuptools<41',
-                negative='setuptools<40',
+                negative='setuptools<41',
             ),
             'docutils==0.14',
             'mock==1.0.1',