No (No mater if you participate as being interviewed or as another interviewer). It is not your function to correct your HR. such questions actually have several functions
- checking how well the candidate actually prepared for the interview
- checking if candidate has an original or good approach to that question
- checking how reacts to a question which he/she considers too simple
- seeing how he/she explains an approach to a non-specialist
While i am also not a friend of some HR people trying to act like they could asses how smart a candidate is by such questions, just let them play theirs games, they are probably aware that the question is well known.