remove discriminator and required from enum - it is set on the using definitions

Author: laithhisham

specification/securityinsights/resource-manager/Microsoft.SecurityInsights/stable/2020-01-01/SecurityInsights.json

@@ -1507,10 +1507,6 @@
     },
     "AlertRuleKind": {
       "description": "The kind of the alert rule",
-      "discriminator": "kind",
-      "required": [
-        "kind"
-      ],
       "enum": [
         "Scheduled",
         "MicrosoftSecurityIncidentCreation",