The pumpkin on snow golems becomes invisible when they have the invisibility effect

Relates to MC-13738 and MC-189840. The pumpkin on snow golems becomes invisible with the invisibility effect, which is inconsistent with the behavior of saddles on pigs and striders. This may be intentional.

Steps to reproduce

1. Create a snow golem
2. Throw an invisibility potion on it

Observed result: The pumpkin is invisible.

Expected result: The pumpkin should remain visible.