ci: bump remaining GitHub Actions to latest (setup-dotnet v5, setup-python v6, upload-artifact v7)

Author: DaveSkender

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
       uses: actions/checkout@v6
 
     - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v4
+      uses: actions/setup-python@v6
       with:
         python-version: ${{ matrix.python-version }}