fixing timestamp decompilation

type:fixed

Checklist:

• Changes follow the existing coding style (use dune @fmt to check).
• Tests for the changes have been added (for bug fixes / feature).
• Documentation has been updated.
• Changelog description has been added (if appropriate).
• Examples in changed behaviour have been added (for breaking change / feature).

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Motivation and Context

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Description

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Changelog description

Changelog details:

fixed decompilation of timestamp in LIGO test