fix(aws-cdk): fix line wrapping issue in YAML

[rix0rrr]

Fix the issue where incorrect UserData was generated by updating to a newer version of the yaml library.

Fixes #1309.

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Pull Request Checklist

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Testing

• Unit test and/or integration test added
• Toolkit change?: integration tests manually executed (paste output to the PR description)
• Init template change?: coordinated update of integration tests (currently maintained in a private repo).

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