doc/go1.10: fix typo of "preserves"

Change-Id: Ib5f5d20200284850c14c2431687bc102696ef8ae
Reviewed-on: https://go-review.googlesource.com/87215Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.10.html

@@ -1223,7 +1223,7 @@ were not indented.
 <dd>
 <p>
 <a href="/pkg/net/url/#ResolveReference"><code>ResolveReference</code></a>
-now preseves multiple leading slashes in the target URL.
+now preserves multiple leading slashes in the target URL.
 Previously it rewrote multiple leading slashes to a single slash,
 which resulted in the <a href="/pkg/net/http/#Client"><code>http.Client</code></a>
 following certain redirects incorrectly.