Upgrading a world last opened in 1.20.4 to 24w18a causes Trial Spawners not working

Description

Upgrading a world with "update 1_21" data pack on in 1.20.4 to either 1.20.6 or 24w18a causes all Trial Spawners not working in neither the two versions.

Steps to Reproduce

1. Create a world in 1.20.4 with "update 1_21" datapack on
2. Place a Trial Spawner and put a mob inside (Spawn Eggs, cmds, etc.)
3. Exit; open the game with either 1.20.6 or 24w18a
4. Select the world and click "Edit," then "Optimize World"
5. Open the world with either versions above and set your Gamemode either Adventure or Survival

(O_o) Trial Spawners spawn mobs as expected.

(×) Trial Spawners do not spawn mobs.