message: [C++] stl_emulation span::count_ is not const anymore
  In C++ we cannot have both assignment operator and const member. Since
  span::operator= is defined, span::count_ constness must be removed.
diff: @@ -466,7 +466,7 @@ class span FLATBUFFERS_FINAL_CLASS {
  private:
  // This is a naive implementation with 'count_' member even if (Extent != dynamic_extent).
  pointer const data_;
  - const size_type count_;
  + size_type count_;
  };
  #endif // defined(FLATBUFFERS_USE_STD_SPAN)
  