fix(stepfunctions-tasks): mwaa service generates wrong action in role…

… policy (#28082)

When we use CallAwsService for Step Functions task, CDK generates IAM policy to grant permission regarding the API call. However, if we specify `mwaa` as service in CallAwsService, CDK generates wrong policy statement such as `mwaa:listEnvironments`. Correct service prefix for MWAA is `airflow`.

https://docs.aws.amazon.com/service-authorization/latest/reference/list_amazonmanagedworkflowsforapacheairflow.html
> Amazon Managed Workflows for Apache Airflow (service prefix: airflow) provides the following service-specific resources, actions, and condition context keys for use in IAM permission policies.

This PR solves the issue by adding `mwaa` into iamServiceMap. This is similar with #27623.

Closes #28081

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