🐛 Bug: README.md additional contents not detected if ALL-CONTRIBUTORS-LIST:END not followed by spellchecker:enable

[JoshuaKGoldberg]

Bug Report Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Expected

Some older CTA repos end their README.md contributors sections with <!-- ALL-CONTRIBUTORS-LIST:END -->, not <!-- spellchecker: enable -->. This should be detected by the logic added in #2088 -> #2090.

Actual

https://github.com/JoshuaKGoldberg/package-json-validator/pull/178/files#r2024947759 shows that it isn't. Only spellchecker: enable comments are detected.

Additional Info

🎁

[github-actions]

🎉 This is included in version v2.22.6 🎉

The release is available on:

• GitHub releases
• npm package (@latest dist-tag)

Cheers! 📦🚀