fix: fix DropdownMenu body handler check to ignore the element itself

fix: fix DropdownMenu body handler check to ignore the element itself

> `andSelf()` is deprecated and should be replaced with `addBack()`
> -- @SassNinja

Also, `andSelf` cannot be used that way. This commit replace it with the opposite approach: checking if the target is the child of the element or the element itself using `closest()`.