scheduled removal of Trainer.running_sanity_check

[Tshimanga]

What does this PR do?

Removes deprecated property Trainer.running_sanity_checking as scheduled for 1.5

Fixes #<issue_number>

Does your PR introduce any breaking changes? If yes, please list them.

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[awaelchli]

@Tshimanga thanks for helping out here!

[radlera]

Hi there,
it seems this PR had a breaking change with the ray[tune] TuneReportCallback.
Are there plans to fix this already?

[awaelchli]

@radlera This was renamed to trainer.sanity_checking.

[awaelchli]

@kaushikb11 makes some updates here as well: ray-project/ray#20562