core: fix doc on build_ceil_floor_function

nac3core/src/toplevel/builtins.rs

@@ -887,7 +887,7 @@ impl<'a> BuiltinBuilder<'a> {
         )
     }
 
-    /// Build the functions `ceil()` and `floor()`.
+    /// Build the functions `ceil()` and `floor()` and their 64 bit variants.
     fn build_ceil_floor_function(&mut self, prim: PrimDef) -> TopLevelDef {
         debug_assert_prim_is_allowed(
             prim,