Add redirect for Flex release note

Author: jpipkin1

cid-redirects.json

@@ -3470,6 +3470,7 @@
   "/release-notes-service/welcome": "/release-notes-service",
   "/release-notes-service/2023/11/27/cis-for-aws": "/release-notes-service/2023/12/31/#november-27-2023-apps",
   "/release-notes-service/2042/06/10/manage": "/release-notes-service/2024/12/31",
+  "/release-notes-service/2024/03/20/flex/": "/release-notes-service/2024/12/31/#march-20-2024-manage",
   "/Send-Data/Applications-and-Other-Data-Sources/Azure-Audit/02Collect-Logs-for-Azure-Audit-from-Event-Hub": "/docs/integrations/microsoft-azure/audit",
   "/Send-Data/Collect-from-Other-Data-Sources/Azure_Monitoring/Collect_Logs_from_Azure_Monitor": "/docs/send-data/collect-from-other-data-sources/azure-monitoring/ms-azure-event-hubs-source/",
   "/Send-Data/Collect-from-Other-Data-Sources/Azure_Monitoring/Collect_Metrics_from_Azure_Monitor": "/docs/send-data/collect-from-other-data-sources/azure-monitoring/collect-metrics-azure-monitor",