content: use Pizza/pizza as an example of exported names

In other languages, all-caps usually signifies an exported constant.
Remove that example since it conflicts with Go's naming guide.

Fixes golang/go#15047.

Change-Id: I7af4a125ad1ba4bd9dd10a0e63eff8e4125cff00
Reviewed-on: https://go-review.googlesource.com/21387
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed