rl-21.03: add PulseAudio 13.0 -> 14.0 upgrade to release notes

nixos/doc/manual/release-notes/rl-2103.xml

@@ -344,6 +344,18 @@
      and rebooting.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     PulseAudio was upgraded to 14.0, with changes to the handling of default sinks.
+     See its <link xlink:href="https://www.freedesktop.org/wiki/Software/PulseAudio/Notes/14.0/">release notes</link>.
+    </para>
+
+    <para>
+     GNOME users may wish to delete their <literal>~/.config/pulse</literal> due to the changes to stream routing
+     logic. See <link xlink:href="https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/832">PulseAudio bug 832</link>
+     for more information.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 </section>