Remove protocol hook option.
Remove protocol hook option.

It's unclear what it would be useful for (compared to other currently
available hooks).

mtth/avsc,N3da/avsc,mtth/avsc,mtth/avsc,N3da/avsc,mtth/avsc,N3da/avsc,N3da/avsc,mtth/avsc,cdapio/ui-schema-parser,cdapio/ui-schema-parser,cdapio/ui-schema-parser,N3da/avsc,cdapio/ui-schema-parser,cdapio/ui-schema-parser