Remove channel field from convert_conversation_to_ticket_request

The channel field should only be added to create_ticket_request and the ticket response schema, not to convert_conversation_to_ticket_request.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: VarshSuresh

descriptions/0/api.intercom.io.yaml

@@ -18189,12 +18189,6 @@ components:
           description: The ID of the type of ticket you want to convert the conversation
             to
           example: '1234'
-        channel:
-          type: string
-          description: The channel for the ticket. Only supported for customer ticket types. Defaults to messenger if not provided.
-          enum:
-          - email
-          example: email
         attributes:
           "$ref": "#/components/schemas/ticket_request_custom_attributes"
       required: