Will getting a gingivectomy affect my porcelain crown?

Possibly: A gingivectomy will remove some of the gum height around the tooth. As the gums heal following the proceedure, they may retract some more. If the crown is a porcelain fused to metal crown, there might be a dark ring visible at the crown margin after the proceedure. If it is an all porcelain crown, the exposed edge would be much less noticeable.

No: A gingivectomy will not affect your porcelain crown but there may be a cosmetic effect if it is a front tooth

Depends: The crown itself will not be affected but the gumline around the crown would be different when the gum is removed. You would need to make sure you keep the area clean. Cosmetically it may look strange if the tooth is in the front of your mouth.