fix (Azure#16164)

Merging the change to have accurate Swagger

Author: msyyc

specification/purview/data-plane/Azure.Analytics.Purview.MetadataPolicies/preview/2021-07-01/purviewMetadataPolicy.json

@@ -41,7 +41,8 @@
           }
         },
         "x-ms-pageable": {
-          "nextLinkName": "nextLink"
+          "nextLinkName": "nextLink",
+          "itemName": "values"
         },
         "x-ms-examples": {
           "MetadataRoles_List": {
@@ -92,7 +93,8 @@
           }
         },
         "x-ms-pageable": {
-          "nextLinkName": "nextLink"
+          "nextLinkName": "nextLink",
+          "itemName": "values"
         },
         "x-ms-examples": {
           "MetadataPolicy_ListAll": {