Update actions/download-artifact action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -105,7 +105,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Download artifacts
-        uses: actions/download-artifact@v3
+        uses: actions/download-artifact@v4
         with:
           name: docs
       - name: Deploy