Update Entity_ListByGuids.json (Azure#17098)

Author: yifan-zhou922

specification/purview/data-plane/Azure.Analytics.Purview.Catalog/preview/2021-05-01-preview/examples/Entity_ListByGuids.json

@@ -1,10 +1,8 @@
 {
   "parameters": {
     "Endpoint": "{Endpoint}",
-    "guid": [
-      "784c0f2f-afd2-e26b-f9cb-984f6c2c5021",
-      "b4ebc8be-cef4-860a-bee9-28cc34cb5caa"
-    ]
+    "guid": "784c0f2f-afd2-e26b-f9cb-984f6c2c5021",
+    "guid": "b4ebc8be-cef4-860a-bee9-28cc34cb5caa"
   },
   "responses": {
     "200": {