The provenance generator GitHub Action generator_generic_slsa3.yml is not compatible with actions/download-artifact@v4 yet. We need to make sure these two Actions and actions/upload-artifact are all compatible.

This PR reverts actions/download-artifact and actions/upload-artifact GitHub Actions to v3. We will update them to v4 when the next version of generator_generic_slsa3.yml that will be compatible with actions/download-artifact@v4 is released. See this relevant slsa-framework/slsa-github-generator#3068.