update actions/deploy-pages to v4

* This hopefully fixes the GitHub actions workflow that currently doesn't find the correct url.

Signed-off-by: Armin Tänzer <[email protected]>

Author: armintaenzertng

.github/workflows/docs.yml

@@ -44,4 +44,4 @@ jobs:
     steps:
       - id: deployment
         name: Deploy docs to GitHub pages
-        uses: actions/deploy-pages@v2
+        uses: actions/deploy-pages@v4