chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/publish.yaml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up quarto
         uses: quarto-dev/quarto-actions/setup@v2
       - name: Publish to GitHub Pages (and render)