no_std/sgx: deps: fix itertools features

[n-prat]

This improves prost(or rather prost-derive) when building in SGX environment.

Without this the dependencies are:

either v1.8.0
└── itertools v0.10.5
    └── prost-derive v0.11.2 (proc-macro)
        └── prost v0.11.3
            └── XXX v0.1.0 (/XXX) (*)

And "either" fails to build under no_std:
cargo no-std-check --manifest-path Cargo.toml:

error[E0463]: can't find crate for `std`
  --> /XXX/.cargo/registry/src/github.com-1ecc6299db9ec823/either-1.8.0/src/lib.rs:19:1
   |
19 | extern crate std;
   | ^^^^^^^^^^^^^^^^^ can't find crate
[...]

I also used the same features for prost-build for consistency, but this is not really required I guess?

[LucioFranco]

Thanks!