Realistically either way is fine. Your options really come down to preference. A. Leave it: this lets the plant use every last bit of energy from the leaf. It also lowers the chance of infection from a dirty cut. B. Cut it off: Often looks better faster and has low risk of infection if you use clean and/or sterilized scissors. Technically allows the plant to not worry abt that leaf anymore and put effort elsewhere but also forces the plant to rapidly attempt to heal.