Ben Gamari authored Apr 24, 2020 and Marge Bot committed May 29, 2020

Now since we no longer try to predict CAFfyness we have no need for the
solution to #16846. Eta expanding unsaturated primop applications is
conceptually simpler, especially in the presence of levity polymorphism.

This essentially reverts cac8dc9f,
as suggested in #18079.

Closes #18079.