Refresh Python dependencies

Author: mdmintz

requirements.txt

@@ -119,7 +119,7 @@ flake8==3.9.2;python_version>="3.5" and python_version<"3.6"
 flake8==4.0.1;python_version>="3.6"
 pyflakes==2.1.1;python_version<"3.5"
 pyflakes==2.3.1;python_version>="3.5" and python_version<"3.6"
-pyflakes==2.4.0;python_version>="3.5"
+pyflakes==2.4.0;python_version>="3.6"
 pycodestyle==2.5.0;python_version<"3.5"
 pycodestyle==2.7.0;python_version>="3.5" and python_version<"3.6"
 pycodestyle==2.8.0;python_version>="3.6"

setup.py

@@ -238,7 +238,7 @@
             'flake8==4.0.1;python_version>="3.6"',
             'pyflakes==2.1.1;python_version<"3.5"',
             'pyflakes==2.3.1;python_version>="3.5" and python_version<"3.6"',
-            'pyflakes==2.4.0;python_version>="3.5"',
+            'pyflakes==2.4.0;python_version>="3.6"',
             'pycodestyle==2.5.0;python_version<"3.5"',
             'pycodestyle==2.7.0;python_version>="3.5" and python_version<"3.6"',  # noqa: E501
             'pycodestyle==2.8.0;python_version>="3.6"',