LPS-47887 Event.target is of type tree-node and does not have attr

Hey Jon, I've reverted this change on `tree_js.jsp` since target in this case is not an `A.Node` so it doesn't have `attr`.

I think I've seen more issues like this coming from the work in https://issues.liferay.com/browse/LPS-44502. I'll let you know if I encounter them again, but maybe you could double check the changed instances to make sure.

Thanks!