nixos/release-notes: render missing docbook

nixos/doc/manual/from_md/release-notes/rl-2111.section.xml

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       </listitem>
       <listitem>
         <para>
+          KDE Plasma now finally works on Wayland.
+        </para>
+      </listitem>
+      <listitem>
+        <para>
           bash now defaults to major version 5.
         </para>
       </listitem>
···
           by default. Both packages now support an
           <literal>enableUnfree</literal> option to re-enable this
           functionality.
+        </para>
+      </listitem>
+      <listitem>
+        <para>
+          <literal>services.xserver.displayManager.defaultSession = &quot;plasma5&quot;</literal>
+          does not work anymore, instead use either
+          <literal>&quot;plasma&quot;</literal> for the Plasma X11
+          session or <literal>&quot;plasmawayland&quot;</literal> for
+          the Plasma Wayland sesison.
         </para>
       </listitem>
     </itemizedlist>