Clean up Strong instance for CoKleisli

Author: aspiwack

src/Data/Profunctor/Kleisli/Linear.hs

@@ -56,8 +56,5 @@ newtype CoKleisli w a b = CoKleisli { runCoKleisli :: w a #-> b }
 instance Data.Functor f => Profunctor (CoKleisli f) where
   dimap f g (CoKleisli h) = CoKleisli (g . h . Data.fmap f)
 
--- instance of a more general idea, but this will do for now
 instance Strong Either Void (CoKleisli (Data.Const x)) where
-  first (CoKleisli f) = CoKleisli (\(Data.Const x) -> (Left :: a #-> Either a b) (f (Data.Const x)))
--- XXX: the above type signature is necessary for certain older versions of
--- the compiler, and as such is temporary
+  first (CoKleisli f) = CoKleisli (\(Data.Const x) -> Left (f (Data.Const x)))