fix: remove redundant zh-Hans i18n overrides causing MDX build failure

The zh-Hans locale is the default locale in Docusaurus config, so docs/doc/
serves zh-Hans content directly. The i18n/zh-Hans/ overrides are unnecessary
and were causing MDX compilation errors during website build.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: JusterZhu