Enable testing CPython 3.9 on Windows

Author: altendky

.github/workflows/ci.yml

@@ -130,10 +130,6 @@ jobs:
               tox: pypy3
             reactor:
               tox: pyside2
-          - python:
-              tox: py39
-            os:
-              python_platform: win32
     steps:
       - uses: actions/checkout@v2
       - name: Enable Problem Matchers