_content/tour: describe any

Instances of interface{} have been replaced by 'any' everywhere in the
standard library, so mentioning it in the tour is a good idea.

Fixes golang/tour#1668

Change-Id: I29d2ba508aa5da0a9c83220ddec1a8f9717a4f8b
Reviewed-on: https://go-review.googlesource.com/c/website/+/818621
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

_content/tour/methods.article

diff --git a/_content/tour/methods.article b/_content/tour/methods.article
index 51a71fe..9e7198e 100644
--- a/_content/tour/methods.article
+++ b/_content/tour/methods.article
@@ -207,8 +207,11 @@
 An empty interface may hold values of any type.
 (Every type implements at least zero methods.)
 
+`any` is an alias for `interface{}`, and the two are completely
+equivalent.
+
 Empty interfaces are used by code that handles values of unknown type.
-For example, `fmt.Print` takes any number of arguments of type `interface{}`.
+For example, `fmt.Print` takes any number of arguments of type `any`.
 
 .play methods/empty-interface.go