typo fix in big_modeling.py #5199

Job	Run time
run-tests (latest, test_prod)	1m 46s
run-tests (latest, test_core)	3m 7s
run-tests (latest, test_cli)	2m 45s
run-tests (latest, test_big_modeling)	2m 34s
run-tests (latest, test_deepspeed)	2m 29s
run-tests (latest, test_fsdp)	2m 33s
run-tests (latest, test_example_differences)	2m 27s
run-tests (latest, test_checkpoint_step)	4m 15s
run-tests (latest, test_checkpoint_epoch)	3m 44s
run-tests (latest, test_rest)	8m 55s
run-tests (minimum, test_prod)	2m 52s
run-tests (minimum, test_core)	4m 24s
run-tests (minimum, test_cli)	4m 12s
run-tests (minimum, test_big_modeling)	3m 41s
run-tests (minimum, test_deepspeed)	3m 34s
run-tests (minimum, test_fsdp)	3m 41s
run-tests (minimum, test_example_differences)	3m 28s
run-tests (minimum, test_checkpoint_step)	5m 4s
run-tests (minimum, test_checkpoint_epoch)	4m 56s
run-tests (minimum, test_rest)	9m 59s
	1h 20m 26s

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