fix: remove unnecessary .json file and unused json import

Author: huiii99

src/azure-cli/azure/cli/command_modules/network/tests/latest/nva-interface-config-example.json

@@ -2,7 +2,6 @@
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for license information.
 # --------------------------------------------------------------------------------------------
-import json
 # pylint: disable=line-too-long
 # pylint: disable=too-many-lines
 import os