Use latest deploy-pages

Related:
* https://github.com/actions/upload-artifact/blob/184d73b71b93c222403b2e7f1ffebe4508014249/README.md#L4
* https://github.com/actions/download-artifact/blob/d0ce8fd1167ed839810201de977912a090ab10a7/README.md#L4

Author: schloerke

.github/workflows/build-docs.yaml

@@ -120,4 +120,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v1
+        uses: actions/deploy-pages@v4