Sync with Synapse: LinkedServiceReference (#19455)

* Sync with Synapse: LinkedServiceReference

* Fix for LinkedService

Author: Frey-Wang

specification/datafactory/resource-manager/Microsoft.DataFactory/stable/2018-06-01/datafactory.json

@@ -5778,13 +5778,18 @@
     },
     "LinkedServiceReference": {
       "description": "Linked service reference type.",
+      "type": "object",
       "properties": {
         "type": {
           "type": "string",
           "description": "Linked service reference type.",
           "enum": [
             "LinkedServiceReference"
-          ]
+          ],
+          "x-ms-enum": {
+            "name": "Type",
+            "modelAsString": true
+          }
         },
         "referenceName": {
           "type": "string",