fix the review comments change x-ms-external to false in sourceControl

Author: xuhumsft

specification/securityinsights/resource-manager/Microsoft.SecurityInsights/preview/2023-10-01-preview/SourceControls.json

@@ -891,7 +891,6 @@
     },
     "Warning": {
       "description": "Warning response structure.",
-      "x-ms-external": true,
       "properties": {
         "warning": {
           "$ref": "#/definitions/WarningBody",
@@ -902,7 +901,6 @@
     },
     "WarningBody": {
       "readOnly": true,
-      "x-ms-external": true,
       "description": "Warning details.",
       "properties": {
         "code": {