Clarify the "Alert" category is for classic alerts

Only classic alerts activations appear in the Activity Log today. Similar support for other alert types is planned for the future.

@bwren, @rboucher - FYI

Author: harelbr

articles/azure-monitor/platform/activity-log-schema.md

@@ -282,7 +282,7 @@ This category contains the record of any resource health events that have occurr
 
 
 ## Alert
-This category contains the record of all activations of Azure alerts. An example of the type of event you would see in this category is "CPU % on myVM has been over 80 for the past 5 minutes." A variety of Azure systems have an alerting concept -- you can define a rule of some sort and receive a notification when conditions match that rule. Each time a supported Azure alert type 'activates,' or the conditions are met to generate a notification, a record of the activation is also pushed to this category of the Activity Log.
+This category contains the record of all activations of classic Azure alerts. An example of the type of event you would see in this category is "CPU % on myVM has been over 80 for the past 5 minutes." A variety of Azure systems have an alerting concept -- you can define a rule of some sort and receive a notification when conditions match that rule. Each time a supported Azure alert type 'activates,' or the conditions are met to generate a notification, a record of the activation is also pushed to this category of the Activity Log.
 
 ### Sample event