prefer_relative_imports should be enabled according to the Dart guides

[tytydraco]

Hello. According to this page on the Dart guide:

When importing a library file from your own package, use a relative path when both files are inside of lib, or when both files are outside of lib. Use package: when the imported file is in lib and the importer is outside.

However, we seem to be using always_use_package_imports. Is there a reason for this?