added docs for Custom LLM Tool Calling Integration (#184)

Author: bajajcodes

fern/calls/call-dynamic-transfers.mdx

@@ -67,21 +67,6 @@ Your server should respond with either a valid `destination` or an `error` to in
 
 ### Transfer Destination Request Response Payload
 
-#### Assistant Destination
-
-```json
-{
-  "destination": {
-    "type": "assistant",
-    "message": "Connecting you to our support assistant.",
-    "assistantName": "SupportAssistant",
-    "transferMode": "rolling-history"
-  }
-}
-```
-
-Transfers the call to another assistant, specifying how the conversation history should be handled.
-
 #### Number Destination
 
 ```json