CI: warnings when building macOS binaries on GA

The build process on GitHub Actions (GA) is warning about versions:

> Warning: This wheel needs a higher macOS version than the version your Python interpreter is compiled against. To silence this warning, set MACOSX_DEPLOYMENT_TARGET to at least 10_13 or recreate these files with lower MACOSX_DEPLOYMENT_TARGET:
> Warning: st.macosx-10.9-universal2/wheel/dss_python_backend/libklusolvex.dylib[WARNING] This wheel needs a higher macOS version than the version your Python interpreter is compiled against. To silence this warning, set MACOSX_DEPLOYMENT_TARGET to at least 10_13 or recreate these files with lower MACOSX_DEPLOYMENT_TARGET:

Since the lowest supported version on GA is 11, if someone has issues in actual usage, please let us know here.

まず、macOS Python wheels をビルドする GitHub Actions workflow と、同梱される libklusolvex.dylib に使用されている deployment-target 設定を調べます。サポート対象の macOS バージョンでビルド警告を再現し、そのうえで、記載されている macOS サポートを維持したまま workflow を警告なしで完了できるか確認します。

索引モデルが issue の本文から書いたものです。