Deprecated for language dialects

[jiesou]

My homeassistant always reports this:

Logger: gtts.lang
Source: components/google_translate/tts.py:107 First seen: 16:45:23 (1 occurrence)
Last seen: 16:45:23 'zh-CN' has been deprecated, falling back to 'zh-CN'. This fallback will be removed in a future version.

I think it has something to do with this:

gTTS/gtts/lang.py

Line 100 in 0f73323

if lang.lower() in deprecated_langs:

It's a case-sensitivity issue, even though "zh-CN" is the correct way, it says "deprecated"

I found a related issue: home-assistant/core#63376

And I noticed that this deprecation is not a recent change, so if this issue originates from downstream (homeassistant) please point it out.