Update ethereum version

[jeremyletang]

The go-ethereum version we are using as of now, is slightly buggy and use a library (go-sigar) which do not support not being build without CGO on macosx at least (other plateform has been fixed).

It seems a recent commit have fixed this behaviour and we should be able to build again without CGO: ethereum/go-ethereum#21041.

Let's try to spend some time to update the dep to the new version.