Remove retired module from learning path

Author: KevSch

learn-pr/paths/az-104-monitor-backup-resources/index.yml

@@ -69,7 +69,6 @@ subjects:
 modules:
 - learn.introduction-to-azure-backup
 - learn.protect-virtual-machines-with-azure-backup
-- learn.azure.intro-to-azure-monitor
 - learn.incident-response-with-alerting-on-azure
 trophy:
   uid: learn.az-104-monitor-backup-resources.trophy

learn-pr/paths/monitor-usage-performance-availability-resources-azure-monitor/index.yml

@@ -26,7 +26,6 @@ products:
 subjects:
 - it-management-monitoring
 modules:
-- learn.azure.intro-to-azure-monitor
 - learn.design-monitoring-strategy-on-azure
 - learn.wwl.monitor-app-performance
 - learn.incident-response-with-alerting-on-azure