Remove unused fast unmarshaller configuration for Dynamodb and DynamodbStreams #481

Job	Run time
check-s3-related-changes	51s
s3-regression-tests-download	2m 20s
s3-regression-tests-control-plane	3m 20s
s3-regression-tests-upload-async	4m 22s
s3-regression-tests-upload-crt	4m 52s
s3-regression-tests-upload-multi	1m 50s
s3-regression-tests-upload-sync	1m 50s
	19m 25s

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