(AzureCXP) fix count of types of schemas supported

Author: PramodValavala-MSFT

articles/event-grid/edge/event-schemas.md

@@ -13,7 +13,7 @@ services: event-grid
 
 # Event schemas
 
-Event Grid module accepts and delivers events in JSON format. There are currently two schemas that are supported by Event Grid: -
+Event Grid module accepts and delivers events in JSON format. There are currently three schemas that are supported by Event Grid: -
 
 * **EventGridSchema**
 * **CustomSchema**
@@ -122,4 +122,4 @@ Refer to [CloudEvents specification](https://github.com/cloudevents/spec/blob/ma
         "dataVersion": "1.0",
         "specVersion": "1.0-rc1"
 }]
-```
+```