Deployment in the sovereign cloud (eusc-de-east-1) fails

When deploying a stack set (that works in `eu-central-1`) in the AWS sovereign cloud (region `eusc-de-east-1`), the deployment fails with:

`Template format error: Unrecognized resource types: [AWS::CDK::Metadata]`

The underlying issue might be similar to (or the same as) this one's: https://github.com/cdklabs/cdk-stacksets/issues/116

Reproduce the stack set deployment in AWS region eusc-de-east-1 and compare it with the working deployment in eu-central-1. Investigate the reported AWS::CDK::Metadata resource error and issue 116; done means the stack set deploys successfully in the sovereign cloud.

Written by the indexing model from the issue text.