Update actions/upload-pages-artifact action to v4

Author: renovate[bot]

.github/workflows/docs.yml

@@ -39,7 +39,7 @@ jobs:
         uses: actions/configure-pages@v5
 
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v4
         with:
           # Upload entire repository
           path: './docs/html'