fix(stepfunctions-tasks): mediapackagevod service generates wrong action in role policy (#28775)

When we use CallAwsService for Step Functions task, CDK generates IAM policy to grant permission regarding the API call. However, if we specify `mediapackagevod` as service in CallAwsService, CDK generates wrong policy statement such as `mediapackagevod:deleteAsset`. Correct service prefix for MediaPackageVOD is `mediapackage-vod`.

https://docs.aws.amazon.com/service-authorization/latest/reference/list_awselementalmediapackagevod.html

> Amazon MediaPackageVOD (service prefix: mediapackage-vod) provides the following service-specific resources, actions, and condition context keys for use in IAM permission policies.

This PR solves the issue by adding mediapackagevod into iamServiceMap. This is similar with #27623 and #28082.

Closes #28774.

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: Nicolas Vaquero