user-modes: Fix incorrect use of keymap mode

The keymap mode was passed to on_next_key_with_autoinfo, which
means the mapping was applied directly by the InputHandler.

That led to the first key being interpretted as a mapping, then
all following keys being executed normally, as if typed in the
parent mode of the user mapping.

src/commands.cc

@@ -2162,7 +2162,7 @@ const CommandDesc enter_user_mode_cmd = {
     {
         KeymapManager& keymaps = get_scope(parser[0], context).keymaps();
         KeymapMode mode = parse_keymap_mode(parser[1], keymaps.user_modes());
-        on_next_key_with_autoinfo(context, mode,
+        on_next_key_with_autoinfo(context, KeymapMode::None,
                                  [mode](Key key, Context& context) mutable {
             if (not context.keymaps().is_mapped(key, mode))
                 return;