The mocked method in Drupal\Tests\Core\Routing\LazyRouteCollectionTest does not return an ArrayIiterator

Problem/Motivation

Method "Symfony\Component\Routing\RouteCollection::getIterator()" will return "\ArrayIterator" as of its next major version. Doing the same in child class "Drupal\Core\Routing\LazyRouteCollection" will be required when upgrading.
    1x in LazyRouteCollectionTest::testGetIterator from Drupal\Tests\Core\Routing

In #3232893: [Symfony 6] Add "ArrayIterator" type hint to the method Drupal\Core\Routing\LazyRouteCollection::getIterator() we added the return type hint to the method Drupal\Core\Routing\LazyRouteCollection::getIterator(), only a mocked method in the test Drupal\Tests\Core\Routing\LazyRouteCollectionTest still return an array.

Steps to reproduce

Proposed resolution

Fix the return value.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet