chore(lang): update zh-TW translations

[SimonAllen0901]

Description

• Add "Playing in Picture-in-Picture" translations to zh-TW.json
• Deduplicate object keys in zh-TW.json
• Update translations-needed.md (auto-generated)

Specific Changes proposed

• Added missing translation for "Playing in Picture-in-Picture" to zh-TW locale.
• Remove duplicate keys 'Picture-in-Picture' and 'Exit Picture-in-Picture' from zh-TW.json to eliminate redundancy.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Change has been verified in an actual browser (Chrome, Firefox, IE)
  • Docs/guides updated
  • Has no DOM changes which impact accessiblilty or trigger warnings (e.g. Chrome issues tab)
  • Has no changes to JSDoc which cause npm run docs:api to error
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.72%. Comparing base (57d6ab6) to head (5bcf643).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8929   +/-   ##
=======================================
  Coverage   83.72%   83.72%           
=======================================
  Files         120      120           
  Lines        8110     8110           
  Branches     1949     1949           
=======================================
  Hits         6790     6790           
  Misses       1320     1320           

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