add xms-ids for PowerBIPrivateLinks (Azure#17973)

Author: LinglingTong

specification/powerbiprivatelinks/resource-manager/Microsoft.PowerBI/stable/2020-06-01/powerbiprivatelinks.json

@@ -911,6 +911,10 @@
           "items": {
             "$ref": "#/definitions/GroupConnectivityInformation"
           },
+          "x-ms-identifiers": [
+            "groupId",
+            "memberName"
+          ],
           "description": "Specifies the group connectivity information of the private link service proxy."
         },
         "remotePrivateLinkServiceConnectionState": {