Upgrade actions/checkout@v5 to @v6 in sample workflows

Co-authored-by: jvdadda <[email protected]>

Author: Copilot

sample/workflows/dockerfile.yml

@@ -19,7 +19,7 @@ jobs:
     name: Dockerfile
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Dockerfile lint
         uses: hadolint/[email protected]
         with: