man: add missing fdstore in systemctl clean --what documentation

(cherry picked from commit 5689365)
(cherry picked from commit cca8e2077f982e5cf636137a92eb7f177a0b4a29)
(cherry picked from commit ae2226ba0d62f9e3132a75639d96211680b337c2)

Author: behrmann

man/systemctl.xml

@@ -554,7 +554,7 @@ Jan 12 10:46:45 example.com bluetoothd[8900]: gatt-time-server: Input/output err
           <term><command>clean <replaceable>PATTERN</replaceable>…</command></term>
 
           <listitem>
-            <para>Remove the configuration, state, cache, logs or runtime data of the specified units. Use
+            <para>Remove the configuration, state, cache, logs, runtime or file descriptor store data of the specified units. Use
             <option>--what=</option> to select which kind of resource to remove. For service units this may
             be used to remove the directories configured with <varname>ConfigurationDirectory=</varname>,
             <varname>StateDirectory=</varname>, <varname>CacheDirectory=</varname>,