[CI] Self-test failure

[github-actions]

Self-test failure

A scheduled test of the workflow has failed.

This suggests one of three conditions:

• A backwards-incompatible change in a Sigstore component;
• A regression in gh-action-sigstore-python;
• A transient error.

The full CI failure can be found here:

https://github.com/sigstore/gh-action-sigstore-python/actions/runs/8832118692

[jku]

502 Server Error: Bad Gateway for url: https://rekor.sigstage.dev/api/v1/log/entries/

This is staging rekor having latency issues after yesterdays mysql upgrade.