Update actions/setup-python action to v6

Author: renovate[bot]

.github/workflows/docs.yml

@@ -28,7 +28,7 @@ jobs:
         run: echo "::add-matcher::.github/matchers.json"
 
       - name: Setup Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: '3.13'