[fix] add option --experimental_allow_proto3_optional

[phuong1492]

Got this error:

 Compiling nexus-network v0.5.1 (/root/.nexus/network-api/clients/cli)
error: failed to run custom build command for `nexus-network v0.5.1 (/root/.nexus/network-api/clients/cli)`

Caused by:
  process didn't exit successfully: `/root/.nexus/network-api/clients/cli/target/release/build/nexus-network-ea227247c6d5a5fd/build-script-build` (exit status: 1)
  --- stdout
  cargo:rerun-if-changed=proto/orchestrator.proto
  cargo:rerun-if-changed=build.rs
  Current dir: "/root/.nexus/network-api/clients/cli"
  Looking for proto file at: "/root/.nexus/network-api/clients/cli/proto/orchestrator.proto"
  protoc is installed and accessible.
  Output directory src/proto exists.
  Error compiling protobuf files: protoc failed: orchestrator.proto: This file contains proto3 optional fields, but --experimental_allow_proto3_optional was not set.

  Error: protoc failed: orchestrator.proto: This file contains proto3 optional fields, but --experimental_allow_proto3_optional was not set.


  --- stderr
  Error: Custom { kind: Other, error: "protoc failed: orchestrator.proto: This file contains proto3 optional fields, but --experimental_allow_proto3_optional was not set.\n" }

Enviroment

Ubuntu 22.04

[aryori]

how to fix this btw?