Use canonical projections.

theories/algebra/sets.v

@@ -3,6 +3,7 @@ From stdpp Require Import countable.
 From iris.algebra Require Export cmra.
 From iris.algebra Require Import updates local_updates.
 Set Default Proof Using "Type".
+Set Primitive Projections.
 
 (** CMRAs for sets with union and disjoint union. *)