Updata securityinsights readme.python (#19917)

* update securityinsights readme.python

* update readme.python

Co-authored-by: Zhenbiao Wei (WICRESOFT NORTH AMERICA LTD) <v-zhenbwei@microsoft.com>

Author: Wzb123456789

specification/securityinsights/resource-manager/readme.python.md

@@ -19,3 +19,11 @@ modelerfour:
 no-namespace-folders: true
 output-folder: $(python-sdks-folder)/securityinsight/azure-mgmt-securityinsight/azure/mgmt/securityinsight
 ```
+
+```
+directive:
+  - from: EntityTypes.json
+    where: $.definitions.AccountEntityProperties.properties.ntDomain
+    transform: >
+        $['description'] = 'The NetBIOS domain name as it appears in the alert format - domain/username. Examples: NT AUTHORITY.';
+```