Add sleep in one auth test

[tnoczyns-volue]

Occasionally[^1] we are getting new token with the same expiration date as the previous one.

test_authentication.py:98: AssertionError

    def test_auth_metadata_plugin_obtains_correctly_new_token_after_delete(
        auth_metadata_plugin,
    ):
        """Check if after deleting access token a new one is correctly obtained."""
        assert auth_metadata_plugin.is_token_valid()
        previous_token = auth_metadata_plugin.token
        previous_token_expiration_date = auth_metadata_plugin.token_expiration_date
        #time.sleep(0.001)
        auth_metadata_plugin.delete_access_token()
        auth_metadata_plugin.get_token()
        new_token = auth_metadata_plugin.token
        new_token_expiration_date = auth_metadata_plugin.token_expiration_date

        assert auth_metadata_plugin.is_token_valid()
        assert new_token is not None
        assert new_token is not previous_token
>       assert previous_token_expiration_date < new_token_expiration_date
E       assert datetime.datetime(2024, 5, 29, 10, 45, 28, 571230, tzinfo=datetime.timezone.utc) < datetime.datetime(2024, 5, 29, 10, 45, 28, 571230, tzinfo=datetime.timezone.utc)

test_authentication.py:99: AssertionError

Add 1ms sleep.

[^1]: I've run into this problem 5 out of 15 times.