Fix a typo in close_functions.

The change fixes what is pretty obviously a typo in `close_functions`: the `uncurried_functions`  list is a list of `(id, params, body, fundesc)` tuples, rather than a list of `(id, params, arity, body)` tuples, as can be seen from the form that creates it as well as from several places it's used.

The typo isn't a bug since the variables `arity` and `body` are never actually referenced in the body of the function, but it does (negatively) affect readability.