fix(i18n): restore zh-CN frontmatter delimiters in AI use cases README

Author: xiaoyijun

i18n/zh-CN/docusaurus-plugin-content-docs/current/use-cases/ai/README.mdx

@@ -1,8 +1,8 @@
 ---
-
 sidebar_position: 3
 sidebar_label: AI
 description: 探索 Logto 如何帮助你构建安全的、支持 AI 的体验。
+---
 
 import Catalog from './fragments/_catalog.mdx';
 import ExploreAiSolutions from './fragments/_explore-ai-solutions.mdx';