Remove SimpleCov from conformance test entrypoints

[landongrindheim]

Summary

This is an attempt to speed up CI a little by removing unused functionality.

SimpleCov was collecting coverage data that codecov couldn't parse 👇, adding overhead to test execution with no benefit. Coverage collection is still available in regular unit tests via the COVERAGE environment variable.

==> Running upload-coverage
      ./codecov upload-coverage -t <redacted> --git-service github --slug sigstore/sigstore-ruby --gcov-executable gcov
info - 2025-10-23 12:09:54,630 -- ci service found: github-actions
warning - 2025-10-23 12:09:54,642 -- No config file could be found. Ignoring config.
warning - 2025-10-23 12:09:54,675 -- xcrun is not installed or can't be found.
warning - 2025-10-23 12:09:54,736 -- No gcov data found.
warning - 2025-10-23 12:09:54,737 -- coverage.py is not installed or can't be found.
info - 2025-10-23 12:09:54,778 -- Found 0 coverage files to report
Error: No coverage reports found. Please make sure you're generating reports successfully.

Release Note

NONE

Documentation

NONE

[woodruffw]

Completely fine by me! @landongrindheim could you add a signoff so that the DCO check passes?

[landongrindheim]

Completely fine by me! @landongrindheim could you add a signoff so that the DCO check passes?

Added the signoff in 93e0cce. I was hoping to see a larger impact on the JRuby/TruffleRuby tests, but the effect was minimal. I think it makes sense to remove since it's not actually uploading results, but I'd be fine closing this if you wanted to see results instead.

I think the Java-based rubies are slowed down by the JVM being started from scratch on each run. I assume that needs to be addressed in sigstore-conformance, but it'd be nice if that could be worked around here.

[woodruffw]

I assume that needs to be addressed in sigstore-conformance, but it'd be nice if that could be worked around here.

Yeah, I believe @loosebazooka was looking at reducing the number of JVM spawns at one point (my memory there is murky though -- that might have been particular to sigstore-java).

[loosebazooka]

Yeah! We already moved sigstore java over to running conformance as a service and the cli calling into it. It's much nicer faster if not a little more complex (but it's an implementation detail of java conformance, not general purpose)