gophertool: fix link to the build status dashboard

R=golang-dev
CC=bradfitz, golang-dev
https://golang.org/cl/5606050

misc/chrome/gophertool/popup.html

@@ -49,6 +49,6 @@ function openURL(url) {
 <a href="#" onclick="openURL('http://code.google.com/p/go/source/list')">commit</a>, or
 <a href="#" onclick="openURL('http://golang.org/pkg/')">pkg</a> id/name:</small>
 <form style='margin: 0' onsubmit="return navigate();"><nobr><input id="inputbox" size=10 /><input type="submit" value="go" /></nobr></form>
-<small>Also: <a href="#" onclick="openURL('http://godashboard.appspot.com/')">buildbots</small>
+<small>Also: <a href="#" onclick="openURL('http://build.golang.org/')">buildbots</small>
 </body>
 </html>