build(deps): bump actions/download-artifact from 4 to 5

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 5.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...v5)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/llgo.yml

@@ -43,7 +43,7 @@ jobs:
         with:
           llvm-version: ${{matrix.llvm}}
       - name: Download model artifact
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v5
         with:
           name: llama2-model
           path: ./_demo/llama2-c/