Lift unused restriction on MonadFail for AllObjects instance of Box Layer

src/PDF/Layer.hs

@@ -55,7 +55,7 @@ instance Output Layer where
 
 data AllObjects = AllObjects
 
-instance MonadFail m => Box m AllObjects Layer (Map ObjectId Object) where
+instance Monad m => Box m AllObjects Layer (Map ObjectId Object) where
   r AllObjects = return . objects
   w AllObjects layer@(Layer {occurrences, docStructure}) newObjects =
     return $ layer {