"Wink" means "shut," and it's clear that Juliet wants eyes to shut because she wants Romeo to come to her "untalk'd of and unseen," like a beautiful dream. What's not clear is why it is "runaways' eyes" that must "wink." Perhaps she's still thinking of the runaway steeds of the sun-chariot when it was driven by Phaëthon. Perhaps she is thinking of herself and Romeo as runaways.