[style](侧边导航栏): 优化侧边导航栏滚动条样式

src/bg-ui/bg-nav-list.vue

 <template>
-  <ul class="nav-list" v-if="list && list.length">
+  <ul class="nav-list bg-no-scroll" v-if="list && list.length">
     <li v-for="(item, index) in list" v-show="item.menuType !== 2" :key="'nav_' + index">
       <template v-if="item.children && item.children.length && item.menuType == 0">
         <div

src/bg-ui/index.scss

@@ -522,7 +522,7 @@ a {
   }
 
   > .bg-nav-list {
-    height: calc(100% - 135px);
+    height: calc(100% - 10px);
     box-sizing: border-box;
 
     ul.nav-list {