exp/cookiejar: update PublicSuffixList doc comment to match the

examples at http://publicsuffix.org/.

That website previously listed pvt.k12.wy.us, but that was an error,
as confirmed by correspondance with submissions@publicsuffix.org, and
the website was fixed on 2013-01-23.

R=adg
CC=dr.volker.dobler, golang-dev
https://golang.org/cl/7241053

src/pkg/exp/cookiejar/jar.go

@@ -16,7 +16,7 @@ import (
 // PublicSuffixList provides the public suffix of a domain. For example:
 //      - the public suffix of "example.com" is "com",
 //      - the public suffix of "foo1.foo2.foo3.co.uk" is "co.uk", and
-//      - the public suffix of "bar.pvt.k12.wy.us" is "pvt.k12.wy.us".
+//      - the public suffix of "bar.pvt.k12.ma.us" is "pvt.k12.ma.us".
 //
 // Implementations of PublicSuffixList must be safe for concurrent use by
 // multiple goroutines.