chore: antd doesn't support IE8 anymore

tests/index.test.js

@@ -1,5 +1,3 @@
-import fs from 'fs';
-import path from 'path';
 import pkg from '../package.json';
 
 describe('antd dist files', () => {
@@ -13,14 +11,6 @@ describe('antd dist files', () => {
   // https://github.com/ant-design/ant-design/issues/1970
   // https://github.com/ant-design/ant-design/issues/1804
   if (process.env.CI) {
-    it('should be compatible in IE8', () => {
-      const antdJsContent = fs.readFileSync(path.join(process.cwd(), 'dist', 'antd.js'));
-      expect(
-        antdJsContent.toString()
-        .indexOf('function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }')
-      ).toBe(-1);
-    });
-
     it('should have antd.version', () => {
       const antd = require('../dist/antd'); // eslint-disable-line global-require
       expect(antd.version).toBe(pkg.version);