Remove deprecated Trainer.slurm_job_id

[awaelchli]

What does this PR do?

Part of #12521

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

Yes

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Make sure you had fun coding 🙃

cc @awaelchli @Borda @justusschock @kaushikb11 @ananthsub @ninginthecloud @jjenniferdai @rohitgr7 @akihironitta

[tchaton]

LGTM !