blog: update URLs for "A Tour of Go"

The URLs to the Go tour were pointing to http://go-tour.appspot.com/,
this changes them to https://tour.golang.org/

Change-Id: Ied9e0440522cdefdccf5a1daf4563add9a62b8dd
Reviewed-on: https://go-review.googlesource.com/c/blog/+/169937
Reviewed-by: Andrew Bonventre <andybons@golang.org>
diff --git a/content/learn-go-from-your-browser.article b/content/learn-go-from-your-browser.article
index 595e6fe..a3cd470 100644
--- a/content/learn-go-from-your-browser.article
+++ b/content/learn-go-from-your-browser.article
@@ -6,10 +6,10 @@
 
 * Introduction
 
-We are excited to announce [[http://go-tour.appspot.com/][A Tour of Go]], a guided tour of the Go programming language you can run from your browser.
+We are excited to announce [[https://tour.golang.org/][A Tour of Go]], a guided tour of the Go programming language you can run from your browser.
 
 The tour is hands-on, demonstrating the language through code samples that you can modify, compile, and run from the tour itself. (The technology behind the [[https://golang.org/doc/play/][Go Playground]] does the work.)
 
 The tour has three sections. The first section covers basic syntax and data structures; the second discusses methods and interfaces; and the third introduces Go's concurrency primitives. Each section concludes with a few exercises so you can practice what you've learned.
 
-So, what are you waiting for? [[http://go-tour.appspot.com/][Get started now!]]
+So, what are you waiting for? [[https://tour.golang.org/][Get started now!]]