Fix zh-CN lang code for Translate feature

[atuchin-m]

The correct chromium code is zh-CN, not zh-Hans.
The backend is fixed here: brave/go-translate#18

For QA: after the fix simplified Chinese pages should be translatable.
Note the for prod users the issue should be fixed by enabling language list update: brave/brave-variations#366
Here the default value in the code should be changed. The default is used until the list is fetched from the backend (for example for restored pages right after the start) or if the fetch is disabled.

[stephendonner]

Verified PASSED using

Brave	1.45.74 Chromium: 106.0.5249.55 (Official Build) beta (x86_64)
Revision	4d5f098fca6ab7f4b6b7c240be3d9593c2357709-refs/branch-heads/5249@{#531}
OS	macOS Version 11.7 (Build 20G817)

1. installed 1.45.74
2. launched Brave
3. loaded each of the sites
4. waited
5. clicked on English to translate

Confirmed I was able to translate Chinese (Simplified) to English.

china.com

Chinese	English

news.cn

Chinese	English

cn.chinadaily.com.cn

Chinese	English

[MadhaviSeelam]

Verification PASSED using

Brave | 1.45.75 Chromium: 106.0.5249.65 (Official Build) beta (64-bit)
-- | --
Revision | 3269dc3633cdd2ab94546fdbe54962e45b17a6e0-refs/branch-heads/5249@{#580}
OS | Windows 11 Version 21H2 (Build 22000.978)

• Install 1.45.75
• launch brave
• loaded each of the sites
• clicked on English to translate and waited
• verified the site has been translated to English from Chinese (Simplified)

bjd.com.cn

Chinese	English

xinmin.cn

Chinese	English

yangtse.com

Chinese	English

Bug filed:

• Chinese to English translation failed few times #25682

[GeetaSarvadnya]

Verification PASSED on Samsung Galaxy Tab A7 version 12 running Bravemonoarm64.apk_1.45.106

1. installed 1.45.106
2. launched Brave
3. loaded each of the sites
4. waited
5. clicked on English to translate

• Confirmed I was able to translate Chinese (Simplified) to English.

china.com

Chinese	English

news.cn

Chinese	English

cn.chinadaily.com.cn

Chinese	English