cmd/present: drop NaCl reference from docs

Change-Id: Ic0b04040ab869c69898a0b7b7b17d1fe624aa4cc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/536135
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

cmd/present/doc.go

@@ -8,9 +8,6 @@ presents slide and article files from the current directory.
 
 It may be run as a stand-alone command or an App Engine app.
 
-The setup of the Go version of NaCl is documented at:
-https://golang.org/wiki/NativeClient
-
 To use with App Engine, copy the files in the tools/cmd/present directory to the
 root of your application and create an app.yaml file similar to this: