[LogsDB] [Subscription basic] [github] Failing test daily: system test: enterprise-audit in github.audit

- Stack version: maximum of either the version used in PR builds or 8.17.0 (GA version for LogsDB index mode)
- LogsDB: enabled
- Subscription: basic
- Package: github
- Failing test: system test: enterprise-audit
- DataStream: audit
- Owners:
- @elastic/security-service-integrations
- @elastic/sit-crest-contractors

Error:
```
could not setup service: could not boot up service using Docker Compose: running Docker Compose up command failed: exit status 18: Head "https://registry-1.docker.io/v2/shourieg/gcs-mock-service/manifests/latest": received unexpected HTTP status: 502 Bad Gateway
```

First build failed: https://buildkite.com/elastic/integrations/builds/49346

Inspect the system test: enterprise-audit in github.audit and its Docker Compose setup for shourieg/gcs-mock-service. Confirm whether the Docker Hub 502 is reproducible; done means the service boots successfully and the test passes reliably.

Written by the indexing model from the issue text.