Call before removing an interactive entity.
When an entity is "unlinked" from the world it remains in memory, but ceases to exist from the point of view of the world.
It disables collision detection for an with the entity.
It also disables any PVS data.
This is useful for temporarily deleting an entity or when performing major alterations to an entity's fields. Unlinking an entity that is already unlinked has no effect.