USE_ICU/libicu lacks any testing or examples

See https://stackoverflow.com/questions/68526626/emscripten-build-with-use-icu-1-and-always-failed-with-u-missing-resource-erro

I'm not sure what to advice this user to do because its not clear what the best way to embed/load the ICU data is.

Unless we add some kind of example or test I think we should remove this port has having something untested/unused like this is probably worse than just having nothing.