Switch to Python 3.8.6 for windows builds on GitHub

.github/workflows/windows-build.yml

@@ -19,7 +19,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: "3.7.9"
+          python-version: "3.8.6"
           architecture: "x86"
 
       - name: Install python tools