Fix a flake in LoggingTest.test_debug_logging.
The jax_debug_log_modules context manager isn't thread-safe, so the test must be marked as thread-unsafe.
I believe this is the cause of this CI flake: https://github.com/jax-ml/jax/actions/runs/23093486364/job/67081949441
PiperOrigin-RevId: 884368926
