Not wrong. I am aware of the other documentary source for what has become the received wisdom of what Voltaire did not actually say.
Most "everyday" quotations are wrong- they are corrupted over time and misuse and if the sense is the same that does not matter too much- but when great minds are quoted by name I feel one should check what they actually did utter before using them in one's defence.
Fortunately, within fell running circles, there is little doubt on the two references I most often use, "...pour encourager les autres...." with regard to the FRA disciplinary process and, of course, "The best is the enemy of the good".