Chapter 2 - Generics - Copy trait not needed anymore (?)

[akiross]

Hello,
first: thank you for the great guide you put together: this gentle intro is very well done and I wish it could be part of the official documentation.

Next, while trying some code from chapter 2, generic functions, I noticed that the generic multiplication does not need the Copy trait (I am using rust 1.37.0). Maybe you could add a short explanation of why that is not needed anymore (if that is the case).

Thanks a lot for all your great work, that I hope you have time to continue :)