fix(firebase_ui_localizations): update and complete Thai (th) translations

[nattapong2041]

Description

Updated and competed Thai(th) language.

Related Issues

none

Checklist

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Breaking Change

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[kevmoo]

/gemini review

[gemini-code-assist]

Code Review

This pull request updates the Thai localizations for Firebase UI, including a grammatical correction for the password reset email text and translations for several other UI strings. A review comment highlights that the @@last_modified timestamp in firebase_ui_th.arb is incorrectly set to a future date and should be updated to reflect the actual modification time.