chore: remove unused registration in test cases

src/count-down/test/index.spec.js

@@ -1,9 +1,6 @@
-import Vue from 'vue';
 import CountDown from '..';
 import { mount, later } from '../../../test';
 
-Vue.use(CountDown);
-
 test('macro task finish event', async () => {
   const wrapper = mount(CountDown, {
     propsData: {