Updated sign, verify & timespan to account timezone.

[scholz-timo]

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Description

This pr is to prevent a error I found whilst using node-jsonwebtoken.
It currently does use the given timezone to generate/validate jwts, but it should be the timestamp without the timezone.

References

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Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• [] All active GitHub checks for tests, formatting, and security are passing
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