message: auth-backend: update FirestoreKeyStore tests to work with Jest 27
diff: @@ -44,6 +44,8 @@ jest.mock('@google-cloud/firestore', () => ({
  Firestore: jest.fn().mockImplementation(() => firestoreMock),
  }));
  +jest.useFakeTimers('legacy');
  +
  describe('FirestoreKeyStore', () => {
  const key = {
  kid: '123',
  @@ -69,11 +71,6 @@ describe('FirestoreKeyStore', () => {
  beforeEach(() => {
  jest.clearAllMocks();
  - jest.useFakeTimers();
  - });
  -
  - afterEach(() => {
  - jest.useRealTimers();
  });
  it('can create an instance without settings', async () => {
  