doc: fix typo in go1.6.html

Change-Id: I7405cf6f65bccbb07a27f2dc2e3802cab591e296
Reviewed-on: https://go-review.googlesource.com/18030Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.6.html

@@ -686,7 +686,7 @@ and
 
 <li>
 Also in the <a href="/pkg/net/http/"><code>net/http</code></a> package,
-there are a few change related to the handling of a
+there are a few changes related to the handling of a
 <a href="/pkg/http/#Request"><code>Request</code></a> data structure with its <code>Method</code> field set to the empty string.
 An empty <code>Method</code> field has always been documented as an alias for <code>"GET"</code>
 and it remains so.