message: Fix incorrect comment.
diff: @@ -572,7 +572,7 @@ Engine &IO::Open(const std::string &name, const Mode mode, helper::Comm comm)
  }
  }
  - // For the inline engine, there must be exactly 1 reader, and exactly 2
  + // For the inline engine, there must be exactly 1 reader, and exactly 1
  // writer.
  if (engineTypeLC == "inline")
  {
  