doc/code.html: fix broken dashboard link

        Fixes #3420.
        Part of issue 3424.

R=golang-dev, cldorian, adg, r
CC=golang-dev
https://golang.org/cl/5958046

doc/code.html

@@ -475,8 +475,8 @@ import "code.google.com/p/go.example/newmath"
 <p>
 This convention is the easiest way to make your Go packages available for
 others to use.
-The <a href="http://godashboard.appspot.com/package">Go Package Dashboard</a>
-displays a list of packages recently installed with the <code>go</code> command.
+The <a href="http://godashboard.appspot.com/project">Go Project Dashboard</a>
+is a list of external Go projects including programs and libraries.
 </p>
 
 <p>