Add possible values to pipeline run status description (Azure#16724)

Author: LijuanZ

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

@@ -5815,7 +5815,7 @@
           "readOnly": true
         },
         "status": {
-          "description": "The status of a pipeline run.",
+          "description": "The status of a pipeline run. Possible values: Queued, InProgress, Succeeded, Failed, Canceling, Cancelled",
           "type": "string",
           "readOnly": true
         },