Update src/Relation/Unary/Properties.agda

Co-authored-by: jamesmckinna <31931406+jamesmckinna@users.noreply.github.com>

Author: mildsunrise

src/Relation/Unary/Properties.agda

@@ -17,7 +17,6 @@ open import Relation.Binary.Definitions
   hiding (Decidable; Universal; Irrelevant; Empty)
 open import Relation.Binary.PropositionalEquality.Core using (refl; _≗_)
 open import Relation.Unary
-import Relation.Nullary.Decidable as Dec
 open import Relation.Nullary.Decidable as Dec using (yes; no; _⊎-dec_; _×-dec_; ¬?; map′; does)
 open import Function.Base using (id; _$_; _∘_)