Add more test coverage to CI Job Token spec

What does this MR do and why?

Adds test coverage for when mutations fail and also found room for improvement for testing when update ci job token scope.

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

Related to #376644 (closed)