doc: minor homepage tweak

Don't imply that the tour isn't browser-based.

R=adg
CC=golang-dev
https://golang.org/cl/5265041

doc/root.html

@@ -51,11 +51,12 @@ google.setOnLoadCallback(loadFeed);
       </p>
       <h2>
         Get started now with
-	<a target="_blank" href="http://go-tour.appspot.com/">A Tour of Go</a>.
+	<a target="_blank" href="http://go-tour.appspot.com/">A Tour of Go</a>
+        in your browser.
       </h2>
       <p>
       <div class="how">[<a href="/doc/playground.html">How does this work?</a>]</div>
-      Or try it right here in your browser:</p>
+      Or try Go right here:</p>
       <div id="playground" class="small"></div>
       <script src="/doc/play/playground.js"></script>
     </div>