Update actions/setup-python action to v6

Author: renovate[bot]

.github/workflows/tests.yaml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v6
         with:
           python-version: "3.13"
       - uses: pre-commit/action@v3.0.1