upgrade gh action (#102)

closes #101

Signed-off-by: Jorge Aguilera <jorge@edn.es>

Author: jagedn

.github/workflows/ghpages.yml

@@ -46,4 +46,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v2
+        uses: actions/deploy-pages@v4