Bug fix for hmac key for V3 #37

Job	Run time
collab-check	5s
wait-for-approval	3s
detect-changes	9s
unit-tests (sagemaker-mlops)	22m 51s
codestyle-doc-tests (sagemaker-core)	19m 59s
unit-tests (sagemaker-core)	28m 54s
integ-tests (sagemaker-core)	10m 37s
codestyle-doc-tests (sagemaker-mlops)	5m 9s
integ-tests (sagemaker-mlops)	20m 22s
	1h 48m 9s

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