Closes #19258: close WSGI server after handling request in demo code.

Author: birkenfeld

Lib/wsgiref/simple_server.py

@@ -155,3 +155,4 @@ def make_server(
     import webbrowser
     webbrowser.open('http://localhost:8000/xyz?abc')
     httpd.handle_request()  # serve one request, then exit
+    httpd.server_close()