fix(firebase_auth): use correct UTC time from server for _webUser.metadata.creationTime & _webUser.metadata.lastSignInTime

[jorgeroncero]

Description

// On firebase-admin (server)
console.log(user.metadata.creationTime); // Mon, 25 Oct 2022 10:17:31 GMT

// As currently implemented
print('${DateFormat('EEE, d MMM yyyy HH:mm:ss', 'en_US').parse(_webUser.metadata.creationTime!)}'); // 2022-10-25 09:17:31.699

// Fix
print('${DateFormat('EEE, d MMM yyyy HH:mm:ss', 'en_US').parse(_webUser.metadata.creationTime!, true)}'); // 2022-10-25 10:17:31.699Z

Related Issues

WEB support to complement PR #9248
Fixes #9162 in WEB

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[Lyokone]

Thanks for the PR :)