adding parameters for dataflow activity (#16603)

Co-authored-by: Bhaskar Annamalai <bhaskara@microsoft.com>

Author: bannama

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

@@ -6704,6 +6704,10 @@
         "datasetParameters": {
           "type": "object",
           "description": "Reference data flow parameters from dataset."
+        },
+        "parameters": {
+          "$ref": "#/definitions/ParameterValueSpecification",
+          "description": "Data flow parameters"
         }
       },
       "additionalProperties": {