Revert "Bump actions/deploy-pages from 3 to 4"

This reverts commit 502923b.

Author: sim642

.github/workflows/docs.yml

@@ -68,4 +68,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v4
+        uses: actions/deploy-pages@v3