Update readme for az iot extension (Azure#16598)

Author: bikamani

sdk/digitaltwins/azure-digitaltwins-core/README.md

@@ -118,5 +118,5 @@ For more information see the Code of Conduct FAQ or contact opencode@microsoft.c
 [token_credential]: https://docs.microsoft.com/java/api/com.azure.core.credential.tokencredential?view=azure-java-stable
 [digital_twins_documentation]: https://docs.microsoft.com/azure/digital-twins/
 [azure_cli]: https://docs.microsoft.com/cli/azure/install-azure-cli?view=azure-cli-latest
-[iot_cli_extension]: https://docs.microsoft.com/azure/iot-pnp/howto-use-iot-pnp-cli
+[iot_cli_extension]: https://github.com/Azure/azure-iot-cli-extension/releases
 [iot_cli_doc]: https://docs.microsoft.com/cli/azure/ext/azure-iot/dt?view=azure-cli-latest