Enabling aquifers in ultrawarm dimensions can generate with water

Enabling aquifers in ultrawarm dimensions (the Nether) can generate with water. This is probably caused by the change that aquifers below Y=0 can be lava aquifers, because it didn't happen before.

Placing the water will make it disappear, but generated water behaves like in the Overworld, even if you do a block update next to it.

Discovered while testing MC-220771.