static/shared/header: change security link

Change the link in navigation to the security documentation root instead
of the subpage on security policies.

For golang/go#57972

Change-Id: Iaf3dc48f15400060c55ea20d2e8372967b88c77e
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/641715
LUCI-TryBot-Result: Go LUCI <[email protected]>
kokoro-CI: kokoro <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: Anna Groebel

static/shared/header/header.tmpl

@@ -42,8 +42,8 @@
                   </li>
                   <li class="go-Header-submenuItem">
                     <div>
-                      <a href="https://go.dev/security/policy/">
-                        <span>Security Policy</span>
+                      <a href="https://go.dev/security/">
+                        <span>Security</span>
                       </a>
                     </div>
                     <p>How Go can help keep you secure by default</p>
@@ -249,8 +249,8 @@
                     </a>
                   </li>
                   <li class="go-NavigationDrawer-listItem">
-                    <a href="https://go.dev/security/policy/">
-                      Security Policy
+                    <a href="https://go.dev/security/">
+                      Security
                     </a>
                   </li>
                 </ul>