Fix link and added missing # (#590)

* Fix link and added missing #

* Update docs/development/SITL.md

* Update docs/development/SITL.md

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

---------

Co-authored-by: Mark Haslinghuis <[email protected]>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

Author: 3 people

docs/development/SITL.md

@@ -163,6 +163,6 @@ To running SITL, you may need to:
 
 ![](/img/sitl/SITL_RF.jpg)
 
-## Customize
+### Customize
 
-If you want to create your own model and extend the SITL, please refer to this [guide](http://www.knifeedge.com/KEmax/) and this [document](https://github.com/xuhao1/RealFlightBridge/blob/main/docs/realflight_protocol).
+If you want to create your own model and extend the SITL, please refer to this [document](https://github.com/xuhao1/RealFlightBridge/blob/main/docs/realflight_protocol.md).