Remove the override WorldTypeRTG#getCloudHeight as it will only affect single-player worlds. Since RTG is not required on the client for multi-player, an instance of WorldTypeRTG will not exist to get the adjusted cloud height from. (Note: Complaint from discord about this not being configurable, but it's best to just remove it and use the vanilla default.)

https://github.com/Team-RTG/Realistic-Terrain-Generation/blob/1.12.2-dev/src/main/java/rtg/world/WorldTypeRTG.java#L69-L72