samples: ipc: Fix incorrect license
Replace Nordic-5-Clause with Apache-2.0.
#
# Copyright (c) 2022 Nordic Semiconductor ASA
#
-# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+# SPDX-License-Identifier: Apache-2.0
#
cmake_minimum_required(VERSION 3.20.0)
