📝 Fix bad link in docs (#1603)

Co-authored-by: lookyun <lookyun0504@outlook.com>

docs/en/docs/advanced/wsgi.md

@@ -1,6 +1,6 @@
 # Including WSGI - Flask, Django, others
 
-You can mount WSGI applications as you saw with [Sub Applications - Behind a Proxy, Mounts](./sub-applications-proxy.md){.internal-link target=_blank}.
+You can mount WSGI applications as you saw with [Sub Applications - Mounts](./sub-applications.md){.internal-link target=_blank}, [Behind a Proxy](./behind-a-proxy.md){.internal-link target=_blank}.
 
 For that, you can use the `WSGIMiddleware` and use it to wrap your WSGI application, for example, Flask, Django, etc.