Added an override to remove() that removes the HoverTextNode event handler from event...

Added an override to remove() that removes the HoverTextNode event handler from event handlers. (fixes #3762)

    @Override
    public void remove() {
        super.remove();
        removeEventHandler(this);
    }

git-svn-id: https://www.simantics.org/svn/simantics/sysdyn/trunk@25957 ac1ea38d-2e2b-0410-8846-a27921b304fc