fix test

Author: kim-em

MathlibTest/ToDual.lean

@@ -32,7 +32,6 @@ structure Lattice (α : Type) extends SemilatticeInf α, SemilatticeSup α
 attribute [to_dual existing] Lattice.toSemilatticeInf
 
 -- we can reorder arguments of arguments in `SemilatticeInf.mk`
-set_option linter.impossibleInstance false in
 @[to_dual, reducible]
 def le_inf_test [Min α] (le_inf : ∀ a b c : α, a ≤ b → a ≤ c → a ≤ b ⊓ c) : SemilatticeInf α where
   le_inf