docs(agent): update custom AI agent examples and remove Dify API support note

- Update Diffy example to Dif example
- Fix CozeAI description from "Dify Example" to "Coze Example"
- Remove note about Dify API support since it's no longer relevant

Author: phodal

docs/agent/custom-ai-agent.md

@@ -54,8 +54,14 @@ Demo:
     "url": "http://127.0.0.1:8765/api/agent/devins-sample",
     "responseAction": "DevIns",
     "defaultTimeout": 20
-  },
-  {
+  }
+]
+```
+
+#### Dif Example
+
+```json
+{
     "name": "DifyAI",
     "description": "Dify Example",
     "url": "https://api.dify.ai/v1/completion-messages",
@@ -68,20 +74,17 @@ Demo:
       "responseFormat": "$.answer"
     },
     "responseAction": "Stream"
-  }
-]
+}
 ```
 
-Notes: Dify API support by [#251](https://github.com/unit-mesh/auto-dev/issues/251), since 1.8.18 version
-
 #### Coze Example
 
 
 ```json
 [
   {
     "name": "CozeAI",
-    "description": "Dify Example",
+    "description": "Coze Example",
     "url": "https://api.coze.cn/v3/chat",
     "auth": {
       "type": "Bearer",