private synchronized void onPluginRemoved(final PluginData pluginData) {
        // copy a new plugin list.
        List<ShenyuPlugin> newPluginList = new ArrayList<>(this.plugins);
        newPluginList.removeIf(plugin -> plugin.named().equals(pluginData.getName()));
        this.plugins = newPluginList;
    }
handle removed or disabled plugin.

@param pluginData plugin data
shenyu-web/src/main/java/org/apache/shenyu/web/handler/ShenyuWebHandler.java