Fix link in documentation

docs/api/mg_set_auth_handler.md

@@ -26,7 +26,7 @@ The callback function can return **0** to deny access, and **1** to allow access
 To allow maximum flexibility in the HTTP response status code and message when denying access, the callback should
 send the HTTP response itself. 
 The callback may send use [`mg_send_digest_access_authentication_request`](mg_send_digest_access_authentication_request.md) to ask for http digest authentication,
-it may send a http 403 status code using `mg_send_http_error`](mg_set_request_handler.md), 
+it may send a http 403 status code using [`mg_send_http_error`](mg_set_request_handler.md), 
 or a 303 redirect to a login page using [`mg_send_http_redirect`](mg_send_http_redirect.md) 
 or any other response.