doc: Add D-Bus RemoveAllNetworks() method

Commit 7c49fdd0bd214f5fa3af8407d7011930ac150ef1 ('dbus: Add
RemoveAllNetworks to the new D-Bus API') added this, but forgot to
document it.

Signed-off-by: Jouni Malinen <j@w1.fi>

doc/dbus.doxygen

@@ -255,6 +255,11 @@ fi.w1.wpa_supplicant1.CreateInterface.
 	</dl>
       </li>
 
+      <li>
+	<h3>RemoveAllNetworks ( ) --> nothing</h3>
+	<p>Remove all configured networks from the interface.</p>
+      </li>
+
       <li>
 	<h3>SelectNetwork ( o : network ) --> nothing</h3>
 	<p>Attempt association with a configured network.</p>