Shaving is fine before breast augmentation. I would however, hold off for about 48 hours before your surgical date in case you break the skin and cause a skin irritation or worse a small infection. Congrats on setting the date for the breast augmentation.
Shaving the skin immediately prior to surgery has been shown to increase the risk of a surgical site infection, which would conclude that shaving immediately prior to surgery can introduce bacteria into the skin and potentially the bloodstream. I assume you will be shaving areas other than your breasts and you should be fine, but I would recommend doing so at least 24 hours before your surgery, 48 if possible, and then not shaving again for at least a couple days after surgery. Check with your surgeon for his/her specific recommendations. Best of luck with your surgery!