The biome features of pale gardens are not experimental

In worlds with the Winter Drop experiment disabled, attempting to place pale garden features using /place succeeds, even though most placed blocks are disabled.

How to reproduce:

1. Create or enter a world with the Winter Drop experiment disabled.
2. Execute one of the following commands:

   /place feature minecraft:pale_garden_vegetation
   /place feature minecraft:pale_moss_patch_bonemeal
   /place feature minecraft:pale_moss_vegetation
   /place feature minecraft:pale_oak
   /place feature minecraft:pale_oak_creaking

Expected result:

It would be impossible to place pale garden features using /place when the Winter Drop experiment is disabled.

Observed result:

Pale garden features can be placed using /place even when the Winter Drop experiment is disabled, allowing a player in Creative mode to obtain disabled items.