chore: Update withastro action in GH workflow

Author: bnubald

.github/workflows/deploy.yaml

@@ -34,7 +34,7 @@ jobs:
           pip install equadratures
           ./build_docs.sh
       - name: Install, build, and upload your site
-        uses: withastro/action@v3
+        uses: withastro/action@v4
         # with:
           # path: . # The root location of your Astro project inside the repository. (optional)
           # node-version: 20 # The specific version of Node that should be used to build your site. Defaults to 20. (optional)