Fix CWL conformance badge

[adamnovak]

This will fix #5417 by using the new feature in Gitlab 18.9 that lets it search around in some recent pipelines to find the one that actually has the job/artifact you are looking for.

I think it will still be possible to run "too many" pipelines that don't generate the badge artifact, and have it disappear again, but fixing that will probably require another Gitlab bug report.

See https://gitlab.com/gitlab-org/gitlab/-/issues/585158 for the Gitlab bug for this feature having been missing.

Changelog Entry

To be copied to the draft changelog by merger:

• CWL conformance badge in the README should no longer be a broken image link

Reviewer Checklist

• Make sure it is coming from issues/XXXX-fix-the-thing in the Toil repo, or from an external repo.
  • If it is coming from an external repo, make sure to pull it in for CI with:

    contrib/admin/test-pr otheruser theirbranchname issues/XXXX-fix-the-thing
    

  • If there is no associated issue, create one.
• Read through the code changes. Make sure that it doesn't have:
  • Addition of trailing whitespace.
  • New variable or member names in camelCase that want to be in snake_case.
  • New functions without type hints.
  • New functions or classes without informative docstrings.
  • Changes to semantics not reflected in the relevant docstrings.
  • New or changed command line options for Toil workflows that are not reflected in docs/running/{cliOptions,cwl,wdl}.rst
  • New features without tests.
• Comment on the lines of code where problems exist with a review comment. You can shift-click the line numbers in the diff to select multiple lines.
• Finish the review with an overall description of your opinion.

Merger Checklist

• Make sure the PR passed tests, including the Gitlab tests, for the most recent commit in its branch.
• Make sure the PR has been reviewed. If not, review it. If it has been reviewed and any requested changes seem to have been addressed, proceed.
• Merge with the Github "Squash and merge" feature.
  • If there are multiple authors' commits, add Co-authored-by to give credit to all contributing authors.
• Copy its recommended changelog entry to the Draft Changelog.
• Append the issue number in parentheses to the changelog entry.

[mr-c]

Thank you!