It is not a shame. Memorialising the suicide of a famous figure on a banknote is a terrible idea, for obvious reasons.

What happened to Alan Turing was an awful and ignorant evil, but this note is about celebrating his life and achievements. He has been pardoned and modern representatives of the government have apologised for his treatment. Is this enough? Of course not, a man was persecuted and driven to death for no good reason. Adding a coda about his suicide everywhere his name is mentioned won't help him. We simply don't have the power to right this wrong; we can only stay vigilant in the present day and honour the memory of Turing (and countless others) by preventing similar injustice now.

Edited: to remove joke that could be seen in poor taste.