fix(functional-tests): Finx failing tests on train tag 287.1

Because:

* Some functional-tests are failing

This commit:

* Add timeout for the cached heading visible assertion

Closes #FXA-9909

packages/functional-tests/tests/react-conversion/oauthSignin.spec.ts

@@ -79,9 +79,7 @@ test.describe('severity-1 #smoke', () => {
         `${page.url()}&forceExperiment=generalizedReactApp&forceExperimentGroup=react`
       );
 
-      await expect(page).toHaveURL(/oauth\/signin/);
-      await expect(page.locator('#root')).toBeEnabled();
-      await expect(signin.cachedSigninHeading).toBeVisible();
+      await expect(signin.cachedSigninHeading).toBeVisible({ timeout: 15000 });
       // Email is prefilled
       await expect(page.getByText(credentials.email)).toBeVisible();
       await signin.signInButton.click();