Docs say `status_details_codec` defaults to `ProtoStatusDetailsCodec()` but actual default is `None`

[stan-stately]

This means that by default the status details aren't included which is kind of confusing.

ref: https://github.com/vmagamedov/grpclib/blob/62f968a4c84e3f64e6966097574ff0a59969ea9b/grpclib/client.py#L624-L647