[Air] ray.air.callbacks.wandb still exists, but fails on import due to `warn_structure_refactor` no longer existing

[st--]

What happened + What you expected to happen

I was trying out https://github.com/klieret/ray-tune-slurm-demo/ which had not specified the exact version of ray[tune] to use. Running the provided example script failed with

Traceback (most recent call last):
  File ".../ray-tune-slurm-demo/src/rtstest/dothetune.py", line 19, in <module>
    from ray.air.callbacks.wandb import WandbLoggerCallback
  File ".../lib/python3.10/site-packages/ray/air/callbacks/wandb.py", line 2, in <module>
    from ray.tune._structure_refactor import warn_structure_refactor
ModuleNotFoundError: No module named 'ray.tune._structure_refactor'

https://github.com/ray-project/ray/blob/master/python/ray/air/callbacks/wandb.py still exists in the latest version, but the _structure_refactor module that provided the refactor/depreciation warning was removed in dcb0a71 - I'm assuming that a couple of files were missed in #36984 and ought to still be removed.

Versions / Dependencies

2.12, 2.20

Reproduction script

from ray.air.callbacks.wandb import WandbLoggerCallback

Issue Severity

Low: It annoys or frustrates me.