Update Windows build to Qt 6.8.1

Author: AlbrechtL

.github/workflows/windows.yml

@@ -16,7 +16,7 @@ jobs:
       - name: Install Qt
         uses: jurplel/install-qt-action@v4
         with:
-          version: '6.8.0'
+          version: '6.8.1'
           modules: 'qtcharts qtmultimedia qt5compat qtshadertools'
           arch: 'win64_mingw'
           tools: 'tools_mingw1310'