Make sure that policy=user commands have host instead of server arg in docs

We renamed them in ejabberd_command, but forgot to update doc geenerator.

src/ejabberd_commands_doc.erl

@@ -472,7 +472,7 @@ generate_html_output(File, RegExp, Languages) ->
     ok.
 
 maybe_add_policy_arguments(#ejabberd_commands{args=Args1, policy=user}=Cmd) ->
-    Args2 = [{user, binary}, {server, binary} | Args1],
+    Args2 = [{user, binary}, {host, binary} | Args1],
     Cmd#ejabberd_commands{args = Args2};
 maybe_add_policy_arguments(Cmd) ->
     Cmd.