Clean description

Author: VedranZoricic

descriptions/0/api.intercom.io.yaml

@@ -20160,7 +20160,7 @@ components:
             previous:
               type: string
               nullable: true
-              description: Previous value of the CDA (null for older events without this data)
+              description: Previous value of the CDA
               example: PROJ-006
     conversation_attribute_updated_by_user:
       title: Part type - conversation_attribute_updated_by_user