Remove Copy impl from OnceWith
Remove Copy impl from OnceWith

Iterators typically don't implement `Copy` and this shouldn't be an exception.

graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust