github-action: fix snapshoty

[v1v]

What

Fixes the snapshoty to download the artifacts from a different Workflow. v4 supports cross workflow integrations.

Why

https://github.com/elastic/apm-agent-dotnet/actions/runs/8971930401

References:

• https://github.com/actions/download-artifact/issues/3#issuecomment-1894005257
• https://github.blog/changelog/2023-12-14-github-actions-artifacts-v4-is-now-generally-available/
• https://github.com/actions/download-artifact?tab=readme-ov-file#download-artifacts-from-other-workflow-runs-or-repositories