Remove forum post reference from appstore.md (#103)

Removed a forum post reference regarding local application creation tips.

Author: wanghe-fit2cloud

docs/user_manual/appstore/appstore.md

@@ -12,8 +12,6 @@
 
     Users can add custom applications as needed. The 1Panel App Store also supports local applications. For the creation tutorial, please refer to:
     [Submit Custom Application Tutorial](https://github.com/1Panel-dev/appstore/wiki/%E5%A6%82%E4%BD%95%E6%8F%90%E4%BA%A4%E8%87%AA%E5%B7%B1%E6%83%B3%E8%A6%81%E7%9A%84%E5%BA%94%E7%94%A8).
-    You can also refer to the forum post:
-    [1Panel Local Application Creation Tips and Third-Party App Repository Examples](https://bbs.fit2cloud.com/t/topic/640/).
 
 ![img.png](../../img/app/appstore.png)
 {: .browser-mockup}