fix: add serve exit code console

close https://github.com/ant-design/ant-design-pro/issues/9575\?notification_referrer_id\=NT_kwDOAHzrKLIzMDEzMDQ5MzkwOjgxODY2NjQ\&notifications_query\=is%3Aunread\#event-5965333309

tests/run-tests.js

@@ -39,7 +39,7 @@ startServer.stdout.on('data', (data) => {
       },
     );
     testCmd.on('exit', (code) => {
-      console.log(code);
+      console.log('服务已经退出，退出码：', code);
       startServer.kill();
       process.exit(code);
     });