fix: re-enable readonly test case

Author: lucaelin

integration/test-runner/tests/test-failure/browser-tests/fail-unserializable-actual.test.js

@@ -1,6 +1,6 @@
 import { expect } from '../../../../../node_modules/@esm-bundle/chai/esm/chai.js';
 
-xit('readonly actual', function() {
+it('readonly actual', function() {
   const fixture = Object.freeze({x: {}});
   expect(fixture).to.equal(null);
 })