Updates `system_tests_sync/test_default.py` and `system_tests_async/test_default.py` to correctly identify and exempt `google.oauth2.credentials.Credentials` (User Credentials) from failures caused by expired or invalid tokens (`invalid_grant`, `invalid_client`). This prevents system tests from failing when running with expired default user credentials in local or CI environments.

self-assigned this

chalmerlowe changed the title Fix system tests for expired User Credentials fix: system tests for expired User Credentials