Switch type to string enum.

Author: eyw520

descriptions/2.11/api.intercom.io.yaml

@@ -13627,6 +13627,17 @@ components:
           type: string
           description: This includes conversation, email, facebook, instagram, phone_call,
             phone_switch, push, sms, twitter and whatsapp.
+          enum:
+          - conversation
+          - email
+          - facebook
+          - instagram
+          - phone_call
+          - phone_switch
+          - push
+          - sms
+          - twitter
+          - whatsapp
           example: conversation
         id:
           type: string