fix: makes node6 happy

Author: huafu

e2e/jest.config.js

@@ -1,9 +1,8 @@
 const base = require('../jest.config');
 
-module.exports = {
-  ...base,
+module.exports = Object.assign({}, base, {
   rootDir: '.',
   testRegex: '/__tests__/.+\\.(test|spec)\\.ts$',
   coverageDirectory: '<rootDir>/../coverage/e2e',
   snapshotSerializers: ['<rootDir>/__serializers__/test-run-result.ts'],
-};
+});