docs(conversations): fix typo of group-sort demo (#680)

* docs(conversations): fix typo of group-sort demo

* test(conversations): update demo snap

Author: wzc520pyfm

components/conversations/__tests__/__snapshots__/demo-extend.test.ts.snap

@@ -487,7 +487,7 @@ exports[`renders components/conversations/demo/group-sort.tsx extend context cor
     >
       <li
         aria-describedby="test-id"
-        class="ant-conversations-item"
+        class="ant-conversations-item ant-conversations-item-active"
       >
         <span
           aria-label="Conversation 1732204800000"

components/conversations/__tests__/__snapshots__/demo.test.ts.snap

@@ -250,7 +250,7 @@ exports[`renders components/conversations/demo/group-sort.tsx correctly 1`] = `
     >
       <li
         aria-describedby="test-id"
-        class="ant-conversations-item"
+        class="ant-conversations-item ant-conversations-item-active"
       >
         <span
           class="ant-typography ant-typography-ellipsis ant-typography-ellipsis-single-line ant-conversations-label"

components/conversations/demo/group-sort.tsx

@@ -45,7 +45,7 @@ const App = () => {
   };
 
   return (
-    <Conversations style={style} groupable={groupable} defaultActiveKey="demo1" items={items} />
+    <Conversations style={style} groupable={groupable} defaultActiveKey="item1" items={items} />
   );
 };