go.talks: fix build by removing dependency

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/7676044
diff --git a/2012/tutorial/main.go b/2012/tutorial/main.go
index bc0fed1..10fcad6 100644
--- a/2012/tutorial/main.go
+++ b/2012/tutorial/main.go
@@ -1,3 +1,5 @@
+// +build ignore,OMIT
+
 package main
 
 import (