scripts: compliance: Use subprocess.run()
scripts: compliance: Use subprocess.run()

As per the current Python documentation, use subprocess.run() since the
other, older methods are not recommended anymore.

Signed-off-by: Carles Cufi <853081dc8dca4fe6a7e3c984752718b5db36e060@nordicsemi.no>

zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr