Update demos.yml

Author: dpo

.github/workflows/demos.yml

@@ -77,7 +77,7 @@ jobs:
           include(joinpath(pkg_path, "..", "examples", "demo-nnmf-constr.jl"))
         shell: julia --project="examples" --color=yes {0}
       - name: Upload results
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: demos-results
           path: ${{ github.workspace }}/*.pdf