Wrong label of Traditional Chinese on language switch menu

[toto6038]

Associated with pull request #2809

The label for Traditional Chinese (zh-hant) is actually neither in Traditional Chinese nor a common name of the language. The linked PR is intended to fix that.

Environment Details:

• MathJax Version: v2.7.5
• Client OS: Windows 10 21H2 (Build 19044.1387)
• Browser: Chrome v96.0.4664.93