ci: Upgrade docs deployment actions

Seeing this error when deploying docs:

    Error: Missing download info for actions/upload-artifact@v3

It's probably upload-pages-artifact@v1 being deprecated. So upgrade
that. And upgrade the other ones as well - might as well.

Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>

Author: danobi

.github/workflows/docs.yml

@@ -27,11 +27,11 @@ jobs:
           cd book
           mdbook build
       - name: Setup Pages
-        uses: actions/configure-pages@v2
+        uses: actions/configure-pages@v5
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v1
+        uses: actions/upload-pages-artifact@v3
         with:
           path: 'book/book'
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v1
+        uses: actions/deploy-pages@v4