Cleanup useless/duplicated code in gen tools (#15113)

Author: lewiszlw

datafusion/proto-common/gen/src/main.rs

@@ -17,9 +17,6 @@
 
 use std::path::Path;
 
-type Error = Box<dyn std::error::Error>;
-type Result<T, E = Error> = std::result::Result<T, E>;
-
 fn main() -> Result<(), String> {
     let proto_dir = Path::new("proto");
     let proto_path = Path::new("proto/datafusion_common.proto");

datafusion/proto/gen/src/main.rs

@@ -17,9 +17,6 @@
 
 use std::path::Path;
 
-type Error = Box<dyn std::error::Error>;
-type Result<T, E = Error> = std::result::Result<T, E>;
-
 fn main() -> Result<(), String> {
     let proto_dir = Path::new("datafusion/proto");
     let proto_path = Path::new("datafusion/proto/proto/datafusion.proto");
@@ -29,7 +26,6 @@ fn main() -> Result<(), String> {
     let descriptor_path = proto_dir.join("proto/proto_descriptor.bin");
 
     prost_build::Config::new()
-        .protoc_arg("--experimental_allow_proto3_optional")
         .file_descriptor_set_path(&descriptor_path)
         .out_dir(out_dir)
         .compile_well_known_types()