Enable external-helpers by default in tests (#12911)

Co-authored-by: Huáng Jùnliàng <jlhwung@gmail.com>
Co-authored-by: Babel Bot <babel-bot@users.noreply.github.com>

packages/babel-plugin-transform-destructuring/test/fixtures/regression/11210/output.mjs

@@ -1,8 +1,6 @@
-function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
-
 export default class A {
   constructor() {
-    _defineProperty(this, "handle", value => {
+    babelHelpers.defineProperty(this, "handle", value => {
       var _ref = {};
       value = _ref.value;
     });