[FIX] web:tests: remove promise constructor antipattern

Revision on https://github.com/odoo/odoo/commit/141b34f152f36d970d4ff78abe53f563555a8e69

Having async/await as a new promise constructor is an antipattern.

The reason is that it may lead to unnoticed errors: if an inner
promise is rejected, it won't propagate the error to another promise
that will handle the error. As a result, this error becomes unnoticed
and the initial promise is pending indefinitely, which also may lead
to more bugs [1].

[1] https://stackoverflow.com/a/25569299

Closes #43072

addons/web/static/tests/helpers/test_utils_dom.js

@@ -20,9 +20,9 @@ var concurrency = require('web.concurrency');
  *
  * @returns {Promise}
  */
-function returnAfterNextAnimationFrame() {
-    return new Promise(async resolve => {
-        await concurrency.delay(0);
+async function returnAfterNextAnimationFrame() {
+    await concurrency.delay(0);
+    await new Promise(resolve => {
         window.requestAnimationFrame(resolve);
     });
 }