talks: add missing build tag to exclude example code

This was causing go test ./... to fail because it was including
an example file when it should not.

Change-Id: I3646d9ede5e893892068e0712528556f7615cb61
Reviewed-on: https://go-review.googlesource.com/c/141877
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

content/2016/applicative/google-parallel.go

diff --git a/content/2016/applicative/google-parallel.go b/content/2016/applicative/google-parallel.go
index 3411951..a73f950 100644
--- a/content/2016/applicative/google-parallel.go
+++ b/content/2016/applicative/google-parallel.go
@@ -1,3 +1,5 @@
+// +build ignore
+
 package main
 
 import (