Finish cleanup in ui/modalDialog close()

I noticed, that in ui/modalDialog the close function takes a timestamp parameter, which is unused (via redirection). I removed it and all that are calling it, that used the value global.get_current_time() to call it.

The reason it's unused via redirection is, that the only thing it does with timestamp, it calls this.popModal(timestamp). But popModal doesn't take a timestamp parameter anymore, it took it before the refactoring took place, and got removed in 3574c524