add x-ms-enum to servicefabricmanagedcluster (Azure#17509)

Author: ArcturusZhang

specification/servicefabricmanagedclusters/resource-manager/Microsoft.ServiceFabric/preview/2021-11-01-preview/managedcluster.json

@@ -1675,6 +1675,10 @@
       "enum": [
         "Windows"
       ],
+      "x-ms-enum": {
+        "name": "ManagedClusterVersionEnvironment",
+        "modelAsString": true
+      },
       "x-ms-parameter-location": "method"
     },
     "location": {

specification/servicefabricmanagedclusters/resource-manager/Microsoft.ServiceFabric/stable/2021-05-01/managedcluster.json

@@ -1381,6 +1381,10 @@
       "enum": [
         "Windows"
       ],
+      "x-ms-enum": {
+        "name": "ManagedClusterVersionEnvironment",
+        "modelAsString": true
+      },
       "x-ms-parameter-location": "method"
     },
     "locationForClusterCodeVersions": {