Run go generate to generate the latest codecs

Re-generate code by running `go generate` to pick up the latest codecs
added to the codec table.

Most notable codec generated here is the CarIndexSorted codec needed in
go-car v2.

See:
- https://github.com/ipld/go-car
- https://github.com/ipld/go-car/milestone/1
- https://github.com/ipld/go-car/blob/wip-v2/v2/index/index.go

Relates to:
- multiformats/multicodec#220