build: pin Windows GitHub runner to windows-2019

Node.js 14 currently doesn't support building with Visual Studio 2022.
For now, pin the Windows workflow to run on `windows-2019` instead of
`windows-latest`.

PR-URL: #42350
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>

.github/workflows/build-windows.yml

@@ -17,7 +17,7 @@ env:
 
 jobs:
   build-windows:
-    runs-on: windows-latest
+    runs-on: windows-2019
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ env.PYTHON_VERSION }}