Wrong locale for chinese translations

The correct name for the Simplified Chinese translation file should be ChangeRequestTranslations.zh.xml, not ChangeRequestTranslations.zh_CN.xml. Version 1.18 had a translation file recognition issue (see attachment). I have made the following adjustments:
1. Renamed the Simplified Chinese translation file and updated its metadata;
2. Added a Simplified Chinese translation file to the Notifications module.
Testing has confirmed that these changes have successfully resolved the file recognition issue.

https://github.com/xwiki-contrib/application-changerequest/pull/160