message: Modify signature of layout_config().
diff: @@ -204,7 +204,7 @@ class HloModuleConfig {
  std::vector<std::vector<int64>>* mutable_dot_config() { return &dot_config_; }
  - absl::Span<const std::vector<std::vector<int64>>> layout_config() const {
  + const std::vector<std::vector<std::vector<int64>>>& layout_config() const {
  return layout_config_;
  }
  