Try to fix GitHub Actions

Author: tleonhardt

.github/workflows/tests.yml

@@ -20,7 +20,7 @@ jobs:
       run:
         # Use a conditional expression to set the default shell
         # 'cmd' on Windows, 'bash' on other platforms (Linux, macOS)
-        shell: ${{ runner.os == 'Windows' && 'cmd' || 'bash' }}
+        shell: ${{ matrix.os == 'windows-latest' && 'cmd' || 'bash' }}
     steps:
       - name: Check out
         uses: actions/checkout@v6.0.2