fix: remove conflicting property for cron success alert

[k4leung4]

│ Error: Error creating AlertPolicy: googleapi: Error 400: Field alertStrategy.notificationRateLimit had an invalid value of "period 	 { seconds: 3600 }": metric-based alert policies must not specify a notification rate limit
│ 
│   with module.notify-automation.module.populate-apkmetadata-cron.google_monitoring_alert_policy.success[0],
│   on .terraform/modules/notify-automation.populate-apkmetadata-cron/modules/cron/main.tf line 331, in resource "google_monitoring_alert_policy" "success":
│  331: resource "google_monitoring_alert_policy" "success" {
│ 
╵
Error: Process completed with exit code 1.