use python3.9 for windows build pipeline

.github/workflows/release_win.yml

@@ -17,7 +17,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: 3.8
+        python-version: 3.9
         architecture: ${{ matrix.arch }}
     - name: Install dependencies and pyinstall
       run: |