fix version confusion in action

Author: sjohansson

.github/workflows/docs.yml

@@ -38,7 +38,7 @@ jobs:
       continue-on-error: false
 
     - name: Upload artifact
-      uses: actions/upload-pages-artifact@v4
+      uses: actions/upload-pages-artifact@v3
       with:
         path: 'docs/_site'