Trial chambers can generate exposed to the air

The Bug:

Trial chambers can generate exposed to the air.

Here is an example:

Seed: -6984109016527939300
Coordinates: /execute in minecraft:overworld run tp @s 9851.54 -13.63 -144.60 2088.53 45.74

Steps to Reproduce:

1. Generate a world with the seed provided above and teleport to the given coordinates.
2. Look closely at the trial chamber.

Observed Behavior:

Trial chambers can generate exposed to the air.

Expected Behavior:

Trial chambers would not be able to generate exposed to the air.