Update actions/setup-python action to v6

Author: renovate[bot]

.github/workflows/tests.yml

@@ -61,7 +61,7 @@ jobs:
 
     steps:
       - name: Set up Python ${{ matrix.pyversion }}
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.pyversion }}