Modify api spec description of create postmortem attachment (#3654)

Co-authored-by: ci.datadog-api-spec <packages@datadoghq.com>

Author: api-clients-generation-pipeline[bot]

.generator/schemas/v2/openapi.yaml

@@ -77857,7 +77857,16 @@ paths:
         If you have any feedback, contact [Datadog support](https://docs.datadoghq.com/help/).'
   /api/v2/incidents/{incident_id}/attachments/postmortems:
     post:
-      description: Create a postmortem attachment for an incident.
+      description: 'Create a postmortem attachment for an incident.
+
+
+        The endpoint accepts markdown for notebooks created in Confluence or Google
+        Docs.
+
+        Postmortems created from notebooks need to be formatted using frontend notebook
+        cells,
+
+        in addition to markdown format.'
       operationId: CreateIncidentPostmortemAttachment
       parameters:
       - description: The ID of the incident

api/datadogV2/api_incidents.go

@@ -730,6 +730,10 @@ func (a *IncidentsApi) CreateIncidentNotificationTemplate(ctx _context.Context,
 
 // CreateIncidentPostmortemAttachment Create postmortem attachment.
 // Create a postmortem attachment for an incident.
+//
+// The endpoint accepts markdown for notebooks created in Confluence or Google Docs.
+// Postmortems created from notebooks need to be formatted using frontend notebook cells,
+// in addition to markdown format.
 func (a *IncidentsApi) CreateIncidentPostmortemAttachment(ctx _context.Context, incidentId string, body PostmortemAttachmentRequest) (Attachment, *_nethttp.Response, error) {
 	var (
 		localVarHTTPMethod  = _nethttp.MethodPost