doc: release: 3.3: Add note on fixed mcumgr bt sample stack overflow
doc: release: 3.3: Add note on fixed mcumgr bt sample stack overflow

Adds a note about a possible stack overflow with the smp_svr sample
application using the Bluetooth transport being fixed.

Signed-off-by: Jamie McCrae <7c977670495befe33b67661379bf81cc6b3660ab@nordicsemi.no>

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