fix(predictions): use UTC timezone in date formatter

[thisisabhash]

Issue #

aws-amplify/amplify-ui-swift-liveness#189

Description

AWS Amplify UI Liveness users with en_TH locale were observing crashes due to AWS server date being incorrectly formatted. This was occurring due to difference in parsing year in Buddhist Calendar vs. Gregorian calendar. Fix involves setting en_US_POSIX locale and GMT timezone in the date formatter.
https://developer.apple.com/library/archive/qa/qa1480/_index.html

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 67.70%. Comparing base (1732349) to head (d1b8b4b).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...ionsPlugin/Liveness/Service/WebSocketSession.swift	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3965      +/-   ##
==========================================
- Coverage   67.82%   67.70%   -0.12%     
==========================================
  Files        1128     1128              
  Lines       52244    52246       +2     
==========================================
- Hits        35434    35374      -60     
- Misses      16810    16872      +62     

Flag	Coverage Δ
API_plugin_unit_test	70.33% <ø> (ø)
AWSPluginsCore	69.34% <ø> (ø)
Amplify	47.82% <ø> (ø)
Analytics_plugin_unit_test	85.20% <ø> (ø)
Auth_plugin_unit_test	73.73% <ø> (+0.12%)	⬆️
DataStore_plugin_unit_test	83.36% <ø> (-0.89%)	⬇️
Geo_plugin_unit_test	74.86% <ø> (ø)
Logging_plugin_unit_test	63.11% <ø> (ø)
Predictions_plugin_unit_test	35.40% <0.00%> (-0.02%)	⬇️
PushNotifications_plugin_unit_test	88.43% <ø> (ø)
Storage_plugin_unit_test	76.88% <ø> (ø)
unit_tests	67.70% <0.00%> (-0.12%)	⬇️

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