doc: release_notes: 3.3: Add net_pkt stable API change
doc: release_notes: 3.3: Add net_pkt stable API change

Document the stable API change in the net_pkt API along with the
expected action from the existing applications.

Signed-off-by: Robert Lubos <9d28997c6894a2d0321a7bb399169af7ce99b64e@nordicsemi.no>

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