Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/copilot-setup-steps.yml

@@ -17,7 +17,7 @@ jobs:
       contents: read
     steps:
       - name: Check out code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Install Chef
         uses: actionshub/chef-install@main
       - name: Install cookbooks