Transform: AWS::Serverless-2016-10-31 CreateStackSet Not supported in SERVICE_MANAGED permission model

## Summary
As mentioned in https://aws.amazon.com/about-aws/whats-new/2021/04/deploy-cloudformation-stacks-concurrently-across-multiple-aws-regions-using-aws-cloudformation-stacksets/ I figured I would convert an existing Cloudformation template Im using in a stackset to use SAM transform Resources.

## Current Behavior
`sam build --config-env ${DEPLOYMENT_ENV}` - successful
`sam package --config-env ${DEPLOYMENT_ENV}` - successful
`sam deploy --config-env ${DEPLOYMENT_ENV}` - successful as stack
```
aws cloudformation create-stack-set \
--stack-set-name "${APP}" \
--template-body file://packaged.yaml \
--permission-model SERVICE_MANAGED \
--region us-east-1 \
--capabilities CAPABILITY_IAM CAPABILITY_NAMED_IAM CAPABILITY_AUTO_EXPAND \
--parameters "ParameterKey=Environment,ParameterValue=${DEPLOYMENT_ENV}" \
--auto-deployment Enabled=true,RetainStacksOnAccountRemoval=true
```
Error:
An error occurred (ValidationError) when calling the CreateStackSet operation: Transform is not supported in SERVICE_MANAGED permission model

## Expected Behavior
CreateStackSet operation performs successfully using AWS::Serverless-2016-10-31 Transform

Start by reproducing the failure with the supplied sam build, sam package, and aws cloudformation create-stack-set commands, using the AWS::Serverless-2016-10-31 transform and SERVICE_MANAGED permission model. Compare the behavior with a regular stack deployment and determine whether CreateStackSet can accept the transformed template. Done means the command succeeds with the stated capabilities and auto-deployment settings.

Written by the indexing model from the issue text.