chore: remove unused registration in test cases

src/tab/test/index.spec.js

@@ -1,11 +1,6 @@
-import Vue from 'vue';
-import Tab from '..';
 import Tabs from '../../tabs';
 import { mount, later, triggerDrag, mockScrollTop } from '../../../test';
 
-Vue.use(Tab);
-Vue.use(Tabs);
-
 function createWrapper(options = {}) {
   return mount({
     template: `