Icebergs can generate inside of ocean monuments

The Bug:

Icebergs can generate inside of ocean monuments.

Caused by the fix for MC-128668; parts of icebergs can now generate inside ocean monuments (but do not replace it, which is likely intended). This can result in elder guardians suffocating.

Here is an example:

Seed: 1428380131082779128
Coordinates: /execute in minecraft:overworld run tp @s 47732.32 40.00 62488.40 -223.80 -10.65

Steps to Reproduce:

1. Generate a world with the seed provided above and teleport to the given coordinates.
2. Look closely at the iceberg inside the ocean monument.
3. Take note as to whether or not icebergs can generate inside of ocean monuments.

Observed Behavior:

Icebergs can generate inside of ocean monuments.

Expected Behavior:

Icebergs would not be able to generate inside of ocean monuments.