chore(deps): bump actions/download-artifact from 5 to 6

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 5 to 6.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/llgo.yml

@@ -52,7 +52,7 @@ jobs:
         with:
           llvm-version: ${{matrix.llvm}}
       - name: Download model artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: llama2-model
           path: ./_demo/c/llama2-c/

.github/workflows/release-build.yml

@@ -158,7 +158,7 @@ jobs:
         with:
           go-version: ${{ matrix.go-version }}
       - name: Download Platform Artifact
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@v6
         with:
           name: llgo-${{ matrix.goos }}-${{ matrix.goarch }}
           path: .