use Fn:Base64 for template values

[cyrfer]

This is difficult to understand and provides no value:

        UserData:
          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

https://github.com/awslabs/ec2-spot-labs/blob/master/builder-sessions/ec2-asg-with-lt/create-asg-with-lt.yaml#L11

Please consider using the Fn:Base64 intrinsic function so we can understand what is happening there.
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-base64.html