chore(deps): bump actions/download-artifact from 4 to 8 (#330)

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4...v8)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/conformance-weekly.yaml

@@ -128,11 +128,11 @@ jobs:
     if: ${{ !cancelled() && github.repository == 'modelcontextprotocol/php-sdk' }}
     steps:
       - uses: actions/checkout@v6
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           name: server-badge
           path: badges-in
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           name: client-badge
           path: badges-in