Fix step shifting when accumulate gradient (#33673)
* replace total_batched_samples with step while counting grad accum step
* remove unused variable
* simplify condition for update step
* fix format by ruff
* simplify update step condition using accelerator.sync_gradients
* simplify update condition using do_sync_step
* remove print for test
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Co-authored-by: Zach Mueller <muellerzr@gmail.com>
