Bump actions/download-artifact from 7 to 8

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 7 to 8.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v7...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>

.github/workflows/build-WebAPI.yml

@@ -888,7 +888,7 @@ jobs:
       - uses: actions/checkout@v7
         with:
           persist-credentials: false
-      - uses: actions/download-artifact@v7
+      - uses: actions/download-artifact@v8
         with:
           pattern: v2rayN.WebAPI-*
           path: release-assets