chore(ci): fix contracts coverage file upload target

[oXtxNt9U]

Summary

It resolves given file names at root level, while the output is inside contracts/. It happened to work because codecov auto searches coverage files but it's not something we should rely on.

./codecov  upload-coverage -t <redacted> --git-service github --sha 074c882470c8771312e479079d59ad95dc29c38d --slug ArkEcosystem/mainsail --file ./lcov.info --flag contracts --gcov-executable gcov
warning - 2026-07-14 10:05:02,972 -- Some files were not found --- {"not_found_files": ["lcov.info"]}

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged