Add 3.4.0 announcement.

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

Author: igsilya

_includes/side-widgets.html

@@ -4,6 +4,9 @@
   </div>
   <div class="widget-body">
     <ul>
+      <li>
+        <a href="https://mail.openvswitch.org/pipermail/ovs-announce/2024-August/000351.html">Aug 15 2024: Open vSwitch 3.4.0 is now Available!</a>
+      </li>
       <li>
         <a href="https://mail.openvswitch.org/pipermail/ovs-announce/2024-August/000350.html">Aug 05 2024: OVS+OVN '24: Call for Participation</a>
       </li>
@@ -76,9 +79,6 @@
       <li>
         <a href=https://mail.openvswitch.org/pipermail/ovs-announce/2021-December/000286.html>Dec 17 2021: Open vSwitch 2.16.2, 2.15.3, 2.14.4 and 2.13.6 are available</a>
       </li>
-      <li>
-        <a href=https://mail.openvswitch.org/pipermail/ovs-announce/2021-October/000280.html>Oct 21 2021: Open vSwitch 2.16.1, 2.15.2, 2.14.3, 2.13.5 and 2.12.4 are available</a>
-      </li>
     </ul>
   </div>
 </div>