elementUi NavMenu 导航菜单 去除下划白线

<el-menu
            class="el-menu-vertical-demo menu-left"
            :unique-opened="true"
            v-for="(muen,key) in menuList"
            :key="muen.menuId"
            :collapse="showCollapse"
            :default-openeds="defaultOpen"
            theme="dark"
            //2个事件，请切记，不能写:default-active="defaultActive"，computed: {
            defaultActive(){
                return this.$route.path.replace('/login');//路由替换，将当前的路由替换掉
            }
        },否则点击二级菜单的时候，别的二级菜单会展开，
            @open="handleOpen"
            @close="handleClose"
            :collapse-transition="true"
            router>
            <el-submenu
                :index="muen.menuId"
            >
                <template slot="title">
                    <i :class="</