Protocol Buffer MIME Types hasn't exist in Internet Assigned Numbers Authority (IANA)

This [page](https://protobuf.dev/reference/protobuf/mime-types/) said:
> So the standard MIME types for common protobuf encodings are:
>
> - application/protobuf for serialized binary protos.
> - application/protobuf+json; charset=utf-8 for JSON format protos.

But I can't find those in the https://www.iana.org/assignments/media-types/media-types.xhtml site?