docs: add SSE custom response type example to Moonshot AI custom LLM server documentation

SSE (Server-Sent Events) is now supported as a custom response type for Moonshot AI's custom LLM server. This commit adds an example of how to configure and use SSE for real-time event streaming in your custom LLM server setup, enhancing the documentation with a practical use case.

Author: phodal

docs/customize/custom-llm-server.md

@@ -94,8 +94,6 @@ And the request body will be:
 
 ### Moonshot AI examples
 
-Official Moonshot AI doc: https://platform.moonshot.cn/docs/api-reference
-
 - Custom Response Type：SSE
 - Custom Engine Server：https://api.moonshot.cn/v1/chat/completions 
 - Request body format