samples: subsys: canbus: isotp: fix sample path in Readme.rst
samples: subsys: canbus: isotp: fix sample path in Readme.rst

The path in the readme did not match the sample's real path.

Signed-off-by: Thomas Stranger <289fb7da2789c69f49f06a4b4e006530cf91f1de@outlook.com>

finikorg/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr