add missing `forall` to `count` function in `benches/nixpkgs/lists.ncl`
"%m
= fun pred => foldr (fun x y => if pred x then y else false) true,
- count: (a -> Bool) -> Array a -> Num
+ count: forall a. (a -> Bool) -> Array a -> Num
| doc m%"
Count how many elements of `list` match the supplied predicate
function.
