chore(deps): update actions/setup-python action to v6

Author: renovate[bot]

.github/workflows/lint-test.yaml

@@ -14,7 +14,7 @@ jobs:
       # Python is required because `ct lint` runs Yamale (https://github.com/23andMe/Yamale) and
       # yamllint (https://github.com/adrienverge/yamllint) which requires Python
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
           python-version: '3.13'
           check-latest: true