proto: Add ignored to comment code block

[dangeross]

Fixes errors testing rust generated code from the spark.proto file

test target/debug/build/spark-18e08f87e92ce858/out/spark.rs - operator::rpc::spark::AdaptorPublicKeyPackage (line 2068) ... FAILED

failures:

---- target/debug/build/spark-18e08f87e92ce858/out/spark.rs - operator::rpc::spark::AdaptorPublicKeyPackage (line 2068) stdout ----
error[E0425]: cannot find value `T` in this scope
 --> target/debug/build/spark-18e08f87e92ce858/out/spark.rs:2069:1
  |
3 | T = t * G
  | ^
  |
help: you might have meant to introduce a new binding
  |
3 | let T = t * G
  | +++
help: you might be missing a const parameter
  |
2 | fn main() { #[allow(non_snake_case)] fn _doctest_main_target_debug_build_spark_18e08f87e92ce858_out_spark_rs_2068_0<const T: /* Type */>() {
  |                                                                                                                    +++++++++++++++++++++

error[E0425]: cannot find value `t` in this scope
 --> target/debug/build/spark-18e08f87e92ce858/out/spark.rs:2069:5
  |
3 | T = t * G
  |     ^ not found in this scope

error[E0425]: cannot find value `G` in this scope
 --> target/debug/build/spark-18e08f87e92ce858/out/spark.rs:2069:9
  |
3 | T = t * G
  |         ^ not found in this scope
  |
help: you might be missing a const parameter
  |
2 | fn main() { #[allow(non_snake_case)] fn _doctest_main_target_debug_build_spark_18e08f87e92ce858_out_spark_rs_2068_0<const G: /* Type */>() {
  |                                                                                                                    +++++++++++++++++++++