.subset? is not working properly.

Ruby Version: 4.0.2

When I do:

```ruby
SortedSet.new(['1', '2', '3']).subset?(SortedSet.new(['1', '2']))
 => true 
```

Even

```ruby
SortedSet.new([1, 2, 3]).subset?(SortedSet.new(['1', '2']))
 => true 
```