doc/1.9: fix broken html link in CL 53030/53210

Change-Id: I7176becd10ad84cbfc3fb9427e190028626e5baf
Reviewed-on: https://go-review.googlesource.com/53291Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.9.html

@@ -477,7 +477,7 @@ version of gccgo.
 
     If any SAN extension, including with no DSN names, is present
     in the certificate, then the Common Name from
-    <a href="#pkg/crypto/x509/#Certificate.Subject"><code>Subject</code></a> is ignored.
+    <a href="/pkg/crypto/x509/#Certificate.Subject"><code>Subject</code></a> is ignored.
     In previous releases, the code tested only whether DNS-name SANs were
     present in a certificate.
     </p>