Resolve Ray deprecation warnings

[tfurmston]

The tests are currently showing some deprecation warnings. These are as follows:

`
tests/tfrlrl/cli/test_sample.py::test_collect_samples_parallel
/Users/thomasfurmston/.pyenv/versions/3.10.16/envs/tfrlrl/lib/python3.10/site-packages/ray/_private/client_mode_hook.py:104: DeprecationWarning: DeprecationWarning: local mode is an experimental feature that is no longer maintained and will be removed in the future. For debugging consider using Ray Distributed Debugger.
return func(*args, **kwargs)

tests/tfrlrl/cli/test_sample.py::test_collect_samples_parallel
/Users/thomasfurmston/.pyenv/versions/3.10.16/envs/tfrlrl/lib/python3.10/site-packages/ray/_private/worker.py:2052: FutureWarning: Tip: In future versions of Ray, Ray will no longer override accelerator visible devices env var if num_gpus=0 or num_gpus=None (default). To enable this behavior and turn off this error message, set RAY_ACCEL_ENV_VAR_OVERRIDE_ON_ZERO=0
warnings.warn(
`

These should be resolved.