Merge pull request #1122 from stan-dev/dependabot/github_actions/actions/checkout-6

Bump actions/checkout from 4 to 6

Author: jgabry

.github/workflows/pkgdown.yaml

@@ -24,7 +24,7 @@ jobs:
     permissions:
       contents: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: r-lib/actions/setup-pandoc@v2