js-on-sx: Object.assign uses js-set-prop so keys appear in __js_order__

lib/js/runtime.sx

@@ -4518,7 +4518,7 @@
                         (for-each
                           (fn
                             (k)
-                            (if (js-key-internal? k) nil (dict-set! target k (get src k))))
+                            (if (js-key-internal? k) nil (js-set-prop target k (get src k))))
                           (js-object-keys src)))
                       ((= (type-of src) "string")
                         (let
@@ -4535,7 +4535,7 @@
       ((>= i n) nil)
       (else
         (begin
-          (dict-set! target (js-to-string i) (char-at s i))
+          (js-set-prop target (js-to-string i) (char-at s i))
           (js-object-assign-string-loop target s (+ i 1) n))))))
 
 (define js-object-freeze (fn (o) o))