Closes#29750. Reporter flagged that 繁體中文 displayed the TW flag
instead of the PRC flag. Rather than picking a side, drop the
language-flag pairings entirely — languages aren't countries
(English ≠ GB, Portuguese ≠ PT, Mandarin variants ≠ any single
jurisdiction), and endonyms are unambiguous.
- LOCALE_META: strip flagCountryCode field
- LanguageSwitcher: remove LocaleFlagIcon component + both call sites
- main.tsx: drop flag-icons CSS import
- package.json: uninstall flag-icons