message: Actually there is no need to copy over the backend config at the Hlo level
diff: @@ -837,10 +837,6 @@ Status HloComputation::ReplaceInstruction(HloInstruction* old_instruction,
  if (new_instruction->metadata().op_name().empty()) {
  new_instruction->set_metadata(old_instruction->metadata());
  }
  - if (new_instruction->raw_backend_config_string().empty()) {
  - new_instruction->set_raw_backend_config_string(
  - old_instruction->raw_backend_config_string());
  - }
  if (new_instruction->frontend_attributes().map().empty()) {
  new_instruction->set_frontend_attributes(
  old_instruction->frontend_attributes());
  