refactor: remove redundant heading from card section in index.mdx

Author: phodal

docs/ai-friendly/index.mdx

@@ -442,8 +442,6 @@ public void deleteBlog(@PathVariable Long id) {
 				</div>
 
 				<div className="card">
-					<h3 className="text-2xl font-bold mb-6 text-center">重构工具的作用</h3>
-
 					<div className="grid-2">
 						<div>
 							<div className="icon-circle bg-green-600">