Fix bug on codegen in ::prost::Enumeration

[megsdevs]

Fixes tokio-rs#927 and tokio-rs#812, caused by tokio-rs#853.

Reverting the changes until a working implementation + test(s) have been built.

I encourage @Leulz to address this before bringing it back in.

[megsdevs]

Valorem fork of tokio-rs#955

[megsdevs]

draft until resolved compatibility with current version of tonic

[megsdevs]

error[E0277]: the trait bound grpc_codegen::Empty: prost::message::Message is not satisfied
--> /Users/megan/git/trade-api/target/debug/build/valorem-trade-9bf8c220466cd8d7/out/valorem.trade.v1.rs:1706:65
|
1706 | let mut grpc = tonic::server::Grpc::new(codec)
| ------------------------ ^^^^^ the trait prost::message::Message is not implemented for grpc_codegen::Empty
| |
| required by a bound introduced by this call
|
= help: the following other types implement trait prost::message::Message:
bool
i32
i64
u32
u64
f32
f64
prost_types::compiler::Version
and 76 others
= note: required for ProstCodec<FeeStructure, grpc_codegen::Empty> to implement Codec