Mobs despawned by Ominous Trial Spawners drop items with Curse of Vanishing

In 1.21-pre1, mobs despawned by ominous trial spawners now drop picked up items. However, items enchanted with Curse of Vanishing do not vanish as expected.

To reproduce:

1. Create or find a Trial Spawner that spawns zombies
2. Activate the spawner without the Bad Omen or Trial Omen effects
3. /data entity merge @n[type=zombie] {CanPickUpLoot:1b}
4. Give the zombie an armor piece with Curse of Vanishing
5. Drink an ominous bottle to make the Trial Spawner become ominous
6. Watch as the armor piece drops