Update courses-cn.html

Author: riverfor

docs/courses-cn.html

@@ -12,7 +12,7 @@
         <div class="grid grid-cols-1 gap-6">
             <!-- Image 1 -->
             <a href="#" onclick="milib.download('https://edu.qpython.org/static/yhc-startup.png','image/jpg')" class="block bg-white rounded-lg shadow-lg overflow-hidden">
-                <img src="https://qpyio.oss-cn-shenzhen.aliyuncs.com/website/2024/12/qpy-course" width="100%">
+                <img src="https://qpyio.oss-cn-shenzhen.aliyuncs.com/website/2024/12/qpy-course.png" width="100%">
                 <div class="p-4">
                 <p style='padding:0px 10px;color:grey'>截图 & 扫码关注学习应用（服务号：QPython编程）或添加教练（微信号yhc-startup）获得学习帮助</p>
                 </div>