fix: typo

[sukyoung]

The following definitions are not used anywhere:

def $arg_for_param(arg, param) : subst
def $arg_for_param(EXP e, EXP x `: t) = {EXP (x, e)}
def $arg_for_param(TYP t, TYP x) = {TYP (x, t)}
def $arg_for_param(FUN y, FUN x `: p* `-> t) = {FUN (x, y)}
def $arg_for_param(GRAM g, GRAM x `: p* `-> t) = {GRAM (x, g)}

def $args_for_params(arg*, param*) : subst
def $args_for_params(eps, eps) = {}
def $args_for_params(a_1 a*, p_1 p*) = s ++ $args_for_params(a*, $subst_param(s, p)*)
  -- if s = $arg_for_param(a_1, p_1)```

[rossberg]

Thanks!

Yeah, the args-for-params is not needed atm. Feel free to remove it.