fix(auth, android): do not timezone offset when getting UTC timestamp

[kouheiszk]

Description

In Android, JWT's iat and exp are now converted to correctly UTC time in strings.
Unnecessary offsets were being added to the timestamps, causing them to be converted to the wrong UTC time in strings.

Related issues

Release Summary

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
• My change includes tests;
  • e2e tests added or updated in packages/\*\*/e2e
  • jest tests added or updated in packages/\*\*/__tests__
• I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • Yes
  • No

Test Plan

I have tested the following:

• The JWT iat was correctly converted to UTC time.
• The JWT exp was correctly converted to UTC time.

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[codecov]

Codecov Report

Merging #4886 (ca14897) into master (c832407) will not change coverage.
The diff coverage is n/a.

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  Lines        3720     3720           
  Branches      347      347           
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  Hits         3313     3313           
  Misses        365      365           
  Partials       42       42           

[mikehardy]

Hi there! Thanks for this, I think you are on to something but we need to be careful with shared APIs

I left a comment related to the other consumers of the shared API you modified - can you have a look at it and tell me what you think?