http2/h2demo: Update some links left dangling after the bradfitz/http2 -> x/net/http2 move.

Change-Id: Idd45c1be493f4535d73323fc2feda5efff45763e
Reviewed-on: https://go-review.googlesource.com/15243
Reviewed-by: Andrew Gerrand <adg@golang.org>

http2/h2demo/h2demo.go

@@ -73,12 +73,12 @@ href="https://http2.github.io/">HTTP/2</a> demo & interop server.</p>
 <p>This server exists for others in the HTTP/2 community to test their HTTP/2 client implementations and point out flaws in our server.</p>
 
 <p> The code is currently at <a
-href="https://golang.org/x/net/http2">github.com/bradfitz/http2</a>
+href="https://golang.org/x/net/http2">golang.org/x/net/http2</a>
 but will move to the Go standard library at some point in the future
 (enabled by default, without users needing to change their code).</p>
 
 <p>Contact info: <i>bradfitz@golang.org</i>, or <a
-href="https://golang.org/x/net/http2/issues">file a bug</a>.</p>
+href="https://golang.org/issues">file a bug</a>.</p>
 
 <h2>Handlers for testing</h2>
 <ul>