content: remove reference to new keyword

The slide about the `new` function was removed in 7f9714c.

Fixes golang/go#12891

Change-Id: I8d192a8261f5ab7eea8f0a677bd367503e023cc8
Reviewed-on: https://go-review.googlesource.com/15753
Reviewed-by: Andrew Gerrand <adg@golang.org>
1 file changed