I thought it was quite compact already, what do you think should be the message?

1) "The link was copied to clipboard"
2) "https://goo.gl/____ was copied"
3) "Success!"
4) Something else?

ps. You can edit your comment and add a reply to this question.

pps. I think the notification is quite important because it is only triggered when the link is copied, which becomes relevant in slower or problematic connections.